Case 40-2004 — A 42-Year-Old Woman with Long-Standing Hematuria
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《新英格兰医药杂志》
Presentation of Case
A 42-year-old woman visited the nephrology clinic for an evaluation of chronic microscopic hematuria.
Microscopic hematuria had been detected 14 years earlier during an episode of cystitis. She subsequently had several episodes of cystitis each year, but the hematuria persisted after treatment and resolution of the infections; usually there were 10 to 20 red cells per high-power field on examination of the urine, but occasionally more than 100, with findings of trace to 1+ proteinuria. An intravenous pyelogram obtained at the time of the initial diagnosis of hematuria was said to have shown a urethral stricture. Ten years before the current evaluation, a urologist prescribed daily nitrofurantoin to prevent recurrent urinary tract infections. A renal ultrasonographic examination prompted by the persistent microscopic hematuria showed normal-size kidneys, no hydronephrosis, and no evidence of renal stones. Cytologic examination of the urine showed no malignant cells.
Later that year, the patient's first pregnancy was complicated by gestational diabetes, which was controlled by diet, and by preeclampsia with a blood pressure of 150/95 mm Hg. Labor was induced, and the delivery was uncomplicated. A second pregnancy three years later was uncomplicated. Nine months after the second delivery, mild hypertension developed; systolic blood pressure ranged between 120 and 144 mm Hg and diastolic pressure ranged between 70 and 96 mm Hg over the next three years. Hematuria and intermittent proteinuria persisted. Another renal ultrasonogram was obtained and showed the right kidney to be 9.3 cm long and the left kidney to be 9.4 cm long without hydronephrosis. No residual fluid was seen within the urinary bladder after voiding. A nephrology consultation was requested.
The patient was a native of the Philippines and had emigrated to the United States at 26 years of age. She worked as a nurse. When she came to the nephrology clinic, she had not had an episode of cystitis for three years. A thyroidectomy for goiter was performed when she was 13 years of age, after which she was prescribed levothyroxine (0.125 mg per day). Her father had had hypertension and had died at the age of 72 from a stroke. Her mother was alive and had diabetes. Her brother died at 46 years of age while on dialysis, of renal failure that was reportedly caused by the use of analgesic agents for the treatment of chronic gout. Two sisters were said to have hematuria; one of them had hypertension, and the other a history of goiter. The patient's two daughters were well.
On physical examination, the patient's weight was 57.2 kg (126 lb), the blood pressure 138/88 mm Hg, and the pulse 72 beats per minute. The results of a physical examination were normal, except for scars from thyroid surgery. The results of a complete blood count, measurements of glucose and electrolyte levels, renal-function tests, measurement of serum immunoglobulin levels, protein electrophoresis, and tests for cryoglobulins, complement, antinuclear antibodies, rheumatoid factor, and urinary Bence Jones protein were normal. Serologic tests were positive for hepatitis B antibody, negative for hepatitis B antigen, and negative for hepatitis C antibodies. Urinalysis disclosed 20 to 50 red cells per high-power field and 1+ proteinuria. Microscopical examination of the urinary sediment disclosed dysmorphic red cells and two cellular casts thought to be red-cell casts. Treatment with lisinopril, 5 mg daily, was prescribed. A 24-hour urine collection of 1600 ml contained 1152 mg of creatinine and 160 mg of protein. At follow-up examinations, five weeks and eight weeks later, the blood pressure was 100/60 and 110/60 mm Hg, respectively.
A diagnostic procedure was performed.
Differential Diagnosis
Dr. David J.R. Steele: This patient presented to me in the clinic with long-standing microscopic hematuria, low-grade proteinuria, a history of mild hypertension, preserved renal function, and a family history of renal disease. Microscopic hematuria is generally defined as more than one to three red cells per high-power field in a centrifuged urine specimen. It has a broad differential diagnosis. In patients with hematuria without proteinuria, approximately 10 percent of cases are due to a glomerular process and the remaining cases are due to urologic factors, although estimates vary widely. In many cases, no cause is found despite extensive evaluation.1,2
Nonglomerular Causes of Microscopic Hematuria
Nonglomerular causes of microscopic hematuria involving the kidney and urinary tract include neoplasms of the kidney, the collecting system, the ureter, and the bladder; nephrolithiasis; cystic diseases; papillary necrosis; hypercalciuria; hyperuricosuria; and sickle cell disease. A urologic workup of this patient included a normal intravenous pyelogram and renal ultrasound imaging that showed kidneys that appeared normal and no evidence of a renal mass lesion. Cytologic examination of the urine was normal. Cystoscopy had not been performed, presumably because there were no risk factors for bladder cancer. Helical computed tomographic (CT) imaging either with or without contrast material — currently the imaging method of choice for diagnosing either a kidney stone or an occult cancer of the upper urinary tract, and more sensitive than ultrasonography — had not been done in this patient.
The crux of this patient's initial evaluation was the microscopical examination of the urine sediment. The sediment contained dysmorphic red cells and red-cell casts. These findings help us differentiate between hematuria arising from a glomerular source and hematuria from a nonglomerular source. Dysmorphic red cells, or acanthocytes, are red cells that have undergone microtrauma while traversing a diseased glomerular basement membrane; such trauma results in structural changes, including loss of biconvexity and the appearance of membrane blebs. Dysmorphic red cells are best seen during phase-contrast microscopical examination of a centrifuged urine sediment (Figure 1A and Figure 1B).
Figure 1. Dysmorphic Red Cells in Urinary Sediment.
Panel A shows red-cell casts (arrow) similar to the one seen in this patient. Panel B shows dysmorphic red cells (arrows), indicative of a glomerular lesion. (Photomicrographs from other patients, courtesy of Dirk Hentschel, Department of Nephrology, Massachusetts General Hospital.)
The reliability of dysmorphic red cells — on their own — as a predictor of glomerular disease in the absence of red-cell casts is controversial.3,4 However, the combination of dysmorphic red cells and red-cell casts is believed to pinpoint a glomerular origin of hematuria; this diagnosis is more likely to be valid if proteinuria is present. In this case, the level of proteinuria was below that which is ordinarily considered clinically significant (300 mg per 24-hour collection, or a protein-to-creatinine ratio of 0.3). Nevertheless, the combination of findings suggested hematuria of a glomerular origin.
Glomerular Causes of Microscopic Hematuria
Once the glomerulus has been defined as the source of hematuria, the differential diagnosis can be narrowed to a limited number of disease processes (Table 1). The probability that this patient had focal glomerulonephritis was small, because of her prolonged hematuria, the minimal proteinuria, her stable normal renal function, and the negative serologic workup. Her clinical presentation was not consistent with a collagen vascular process, anti–glomerular basement membrane disease, or vasculitis. Tests for hepatitis B surface antigen and hepatitis C antibody were negative. The long natural history in the absence of clinically significant proteinuria and hypertension is not consistent with poststreptococcal glomerulonephritis.
Table 1. Differential Diagnosis of Isolated Hematuria of Glomerular Origin.
The family history of renal disease suggested the possibility of a hereditary renal disorder. The patient had two sisters who had hematuria and apparently normal renal function; one is said to have had hypertension, although we do not have the details. In addition, her brother died at a young age of end-stage renal disease, with the cause said to be analgesics used to treat gout. We have incomplete records of these events, but we should consider alternative diagnoses, including the possibility that the brother had a hereditary renal disease. Hereditary renal diseases associated with hematuria include Alport's syndrome (hereditary nephritis), thin-basement-membrane nephropathy, polycystic kidney disease, Fabry's disease, the nail–patella syndrome, and possibly — in some kindreds — IgA nephropathy.
IgA Nephropathy
IgA nephropathy is a common cause of microscopic hematuria.5 It results from mesangial IgA deposition. Although some patients have an elevated IgA level, not all do; an increase in IgA level alone is not sufficient to produce this disease. A defect in galactosylation of IgA1 may play a role. A patient who has IgA nephropathy may present with hematuria (with or without proteinuria), hypertension, and a rising serum creatinine level. The natural history of the condition varies among patients, ranging from those who have hematuria with stable renal function to those (between 15 percent and 40 percent in reported studies) in whom end-stage renal disease develops. There are no markers that predict progressive disease in patients who present with only minor urinary abnormalities.6 A subgroup of patients with IgA nephropathy may have hereditary disease. A linkage of IgA nephropathy to chromosome 6q22–23 with a dominant mode of inheritance has been shown.7
Alport's Syndrome
Alport's syndrome is a rare hereditary renal disease caused by a defect in genes coding for the 5 chain of type IV collagen. The majority of cases are X-linked; autosomal recessive inheritance occurs in 5 percent of cases and autosomal dominant inheritance in a few kindreds. The first sign of the disease is microscopic or occasionally macroscopic hematuria. Alport's syndrome occurs predominantly in men, and affected male patients classically have hematuria, proteinuria (urinary protein excretion, less than 1 to 2 g per day), progressive renal failure, and sensorineural deafness. Lenticonus of the anterior lens capsule, retinopathy, and leiomyomatosis are sometimes associated with the disease. Deafness occurs in approximately 55 percent of patients. The urine sediment is likely to contain dysmorphic red cells and red-cell casts. Patients with Alport's syndrome lack a component of glomerular basement membrane, and anti–glomerular basement membrane glomerulonephritis may develop after kidney transplantation. The disorder is clinically variable, probably reflecting the complexity of collagen genetics.8,9
Heterozygous females in families with Alport's syndrome may have intermittent or persistent microscopic hematuria with no other manifestations of renal disease; about 10 percent of heterozygous female patients have no hematuria. Proteinuria is uncommon, as is hypertension. The prognosis for affected girls and women is generally good, but end-stage renal disease develops in some women. In such cases, gross hematuria in childhood, nephrotic-range proteinuria, and thickening of the glomerular basement membrane (identified by the use of electron microscopy) are associated with progressive nephritis. Hearing loss and lenticonus, although rare, are also associated with an adverse outcome in heterozygous female patients. Pregnancy does not appear to have an adverse effect on renal function in patients with mild disease but may accelerate the decline in renal function in those with severe disease.
Thin Basement Membrane Nephropathy
In thin basement membrane nephropathy, also known as benign familial hematuria or thin basement membrane disease, the glomerular basement membrane is uniformly thinned to about half its normal thickness. Many cases follow an autosomal dominant mode of inheritance and, as with Alport's syndrome, are caused by mutations in the type IV collagen gene — in this case the 3 and 4 chains. There is a female-to-male ratio of 1.6. The prevalence of this disease cannot be accurately estimated because of the reluctance of nephrologists to perform a renal biopsy in patients with isolated hematuria, but it is likely that thin basement membrane nephropathy occurs in about 1 percent of the general population.10 Patients present with hematuria; there may be proteinuria, although usually urinary protein excretion is less than 500 mg per day, and hypertension is rare. There are no extrarenal manifestations. Renal failure occurs rarely and, for unclear reasons, often in association with other glomerulonephritides. Focal segmental glomerulosclerosis is reported to occur in at least 5 percent of patients. IgA nephropathy may occur together with thin basement membrane nephropathy — probably more often than by chance alone.11 The diagnosis is based on the combination of hematuria and characteristic changes on renal biopsy and on the finding of hematuria in multiple family members without a history of end-stage renal disease. Treatment is nonspecific and includes control of hypertension, use of angiotensin-converting–enzyme inhibitors if proteinuria or hypertension is present, and modest dietary protein restriction.10,12
Differential Diagnosis of Alport's Syndrome and Thin Basement Membrane Nephropathy
The distinction between thin basement membrane nephropathy and Alport's syndrome is not always easy to make. It is important to distinguish between the two when possible, because of the different prognoses of these conditions and because of the implications for the offspring of the female carriers of Alport's syndrome. Since hearing loss, lenticonus, and retinopathy are found in fewer than 10 percent of female carriers of Alport's syndrome, thin basement membrane nephropathy and Alport's syndrome are difficult to distinguish on clinical grounds alone in women who have hematuria as their only clinical abnormality.13,14
The family history may be useful. A family history of hematuria without renal failure supports a diagnosis of thin basement membrane nephropathy. If the nature of renal failure in a family member is unknown, then information regarding hearing loss or eye disorders may be useful. In the case under discussion, there was no history of either in the brother who had end-stage renal disease. The absence of hearing loss or optical abnormalities, however, does not rule out Alport's syndrome as the cause of end-stage renal disease in his case, since these extrarenal abnormalities are not present in all cases. In questionable cases, a renal biopsy may be helpful.10,12,15,16,17
Role of Renal Biopsy
A renal biopsy is not routinely recommended in the evaluation of patients with isolated microscopic hematuria, unless there is evidence of clinically significant proteinuria or a progressive deterioration in renal function. In their review of microscopic hematuria in the Journal, Cohen and Brown18 recommended against performing a renal biopsy in cases of isolated glomerular microscopic hematuria, since available data suggest that identification of the specific disease does not make a difference in management or outcome. Complications of renal biopsy are infrequent but must be borne in mind. Major bleeding occurs in 1 to 2 percent of the patients who undergo biopsy, and mortality is about 0.1 percent. We accept that not having a tissue diagnosis is valid in most patients with isolated hematuria whose disease is following a benign course. In this case, however, I favored performing a biopsy because of increasing concern on the part of a medically sophisticated patient and our desire to define her underlying diagnosis in the context of her strong family history. The hope was that prognostic information would be obtained that would be reassuring to the patient and her family and that further evaluations could be avoided.
Dr. Nelson Goes (Nephrology): Does the fact that the patient comes from the Philippines alter the evaluation? Are there any tropical diseases that could cause chronic hematuria?
Dr. Steele: In tropical regions there is a high incidence of schistosomiasis, which may be manifested in the patient by lower urinary tract bleeding. It certainly is a consideration under appropriate circumstances.
Dr. David J.R. Steele's Diagnosis
Thin basement membrane nephropathy or X-linked Alport's syndrome or IgA nephropathy.
Pathological Discussion
Dr. Paul J. Michaels: The diagnostic procedure was a percutaneous renal biopsy. The glomeruli were normal when examined by light microscopy, except for focal, mild mesangial hypercellularity (Figure 2A). The interstitium, renal tubules, and vessels were normal. Immunofluorescent staining of the glomeruli showed slight segmental linear staining for IgG and albumin. Only very focal, trace granular staining for IgA and IgM was noted in the mesangium, excluding a diagnosis of IgA nephropathy. Electron-microscopical examination showed diffusely thin glomerular basement membranes (Figure 2B). Some segments were thickened, scalloped, and contained electron-dense granules ("microparticles"), but no definite laminations were seen (Figure 2C). Ultrastructural morphometric analysis revealed a harmonic mean (±SD) glomerular-basement-membrane thickness of 219±20 nm, with a range of 121 to 328 nm. The normal glomerular-basement-membrane thickness in women as measured by this method is 326±45 nm.
Figure 2. Examination of Renal-Biopsy Specimen by Light and Electron Microscopy.
The glomerulus shows a slight increase in the mesangial matrix, with focal mesangial hypercellularity (Panel A) (hematoxylin and eosin). On electron-microscopical examination, the glomerular basement membrane appears diffusely thin (Panel B). Focally, small electron-dense granules (microparticles) are present (arrowheads), and the endothelial portion of the basement membrane is scalloped (Panel C, arrows).
These histologic, immunofluorescent, and ultrastructural findings are consistent with a diagnosis of either thin basement membrane nephropathy or a carrier state of X-linked Alport's syndrome (Table 2). Thin glomerular capillary basement membranes are the only pathological abnormality in the kidneys of patients with thin basement membrane nephropathy.19 However, thin glomerular basement membranes are found in Alport's syndrome and may be the only finding in early Alport's syndrome and in female carriers of X-linked Alport's syndrome. In carriers of X-linked Alport's syndrome, however, there may also be areas of splitting and thickening of the basement membrane, which worsen over time; these abnormal areas are not seen in thin basement membrane nephropathy. In this case, the presence of widespread thin glomerular basement membranes in combination with focal membrane thickening, scalloping, and microparticles suggests that the patient is a carrier of X-linked Alport's syndrome. However, although full-blown Alport's syndrome is therefore excluded, the pathological findings alone are not sufficient to distinguish with certainty between thin basement membrane nephropathy and heterozygosity for an Alport mutation.
Table 2. Common Renal-Biopsy Findings in Conditions Causing Microscopic Hematuria.
The genetic mutations responsible for the phenotypic abnormalities seen in both X-linked and autosomal recessive or dominant Alport's syndrome and thin basement membrane nephropathy have been characterized (Table 3).20,21 These discoveries have enabled pathologists to use ancillary diagnostic techniques to narrow the differential diagnosis in patients with thin glomerular basement membranes. The three clinical entities have in common abnormalities in the chains of type IV collagen (COL4), specifically the 3, 4, and 5 chains, which form a triple helical protomer found in the glomerular basement membrane (Figure 3).8 X-linked Alport's syndrome is typically caused by mutations in the 5 chain of type IV collagen (COL4A5).20 In contrast, autosomal Alport's syndrome, which can be inherited in both a recessive and a dominant fashion, is the result of defects in the genes encoding for either the 3 (COL4A3) or the 4 (COL4A4) subunits of type IV collagen.21 The mutations seen in thin basement membrane nephropathy also frequently involve both the 3 and 4 chains of type IV collagen, suggesting that autosomal Alport's syndrome and thin basement membrane nephropathy may represent points on a spectrum of a single disease process.22 Thus, some persons with thin basement membrane nephropathy may have a single copy of a mutated gene in either the 3 or 4 chain of type IV collagen that, when present in a homozygous form, leads to autosomal recessive Alport's syndrome. Different mutations in these same genes occasionally lead to the less common autosomal dominant Alport's syndrome.
Table 3. Conditions Associated with Thin Basement Membrane on Electron Microscopy and Corresponding Mutations of Type IV Collagen.
Figure 3. Structure of the Chains of Type IV Collagen and Mutations in Renal Disease.
Six distinct chains (left) are arranged into three triple helical protomers composed of different chains (right). Each protomer has a 7S triple helical domain at the N-terminal; a long, triple helical, collagenous domain in the middle of the molecule; and a noncollagenous (NC1) trimer at the C-terminal. The 1, 1, 2 protomer is found in all basement membranes, whereas the 3, 4, 5 and 5, 5, 6 protomers are differentially distributed in various tissues (box). This heterogeneous distribution probably accounts for the variety of overlapping clinical syndromes associated with mutations in different chains. (The illustration has been adapted from Hudson et al.8)
The mutations in Alport's syndrome lead to a segmental reduction in the amount of both 3 and 5 collagen in the glomerular basement membrane; this defect can be detected by immunofluorescence staining with antibodies to these proteins. In contrast, the mutations in the 3 chain in thin basement membrane nephropathy do not produce this pattern. Segmental loss of glomerular staining for the 5 chain of type IV collagen suggests a carrier state for X-linked Alport's syndrome; however, normal staining does not necessarily rule out the diagnosis.23 Additional diagnostic tests include immunofluorescence staining of a skin-biopsy specimen for the 5 chain of type IV collagen. Interrupted staining in a female patient suggests a carrier status for X-linked Alport's syndrome, whereas even, linear staining supports the diagnosis of thin basement membrane nephropathy.24 Finally, sequencing of the gene for the 5 chain of type IV collagen can be performed to confirm or rule out X-linked Alport's syndrome, since this gene is usually unaffected in patients with thin basement membrane nephropathy.
In the patient under discussion, staining of the renal-biopsy specimen with antibodies to the 3 and 5 chains of type IV collagen revealed segmental reduction in the normal linear staining along the glomerular basement membranes for both proteins, as compared with a control glomerulus (Figure 4A and Figure 4B). This segmental reduction in staining for the 3 and 5 chains of type IV collagen further suggests a carrier state for X-linked Alport's syndrome.
Figure 4. Immunofluorescence Staining of Renal-Biopsy Specimens with Antibody for 3 Chains of Type IV Collagen.
Immunofluorescence staining of a specimen from a kidney without disease (Panel A) reveals bright, uninterrupted linear staining for the 3 chain of type IV collagen. However, staining of a specimen from the patient's glomerulus with the same monoclonal antibody reveals an overall decrease in staining intensity, with further segmental reduction of staining in the capillary loops (Panel B, arrows). A similar pattern was seen with the use of an antibody to the 5 chain.
Dr. Steele: Since her evaluation, the patient has been seen in annual follow-up visits. Two years after the diagnostic biopsy, she remains well, with no evidence of progressive renal disease. She continues to receive treatment for hypertension and has microscopic hematuria and stable mild proteinuria. She reports that her daughters have been tested and do not have hematuria. She is in the process of reviewing her diagnosis and its implications with other family members.
Dr. Lynn D. Cornell (Pathology): In the future, with a patient such as this one, would you consider doing a skin biopsy instead of a renal biopsy?
Dr. Steele: Skin biopsy is a much less invasive procedure than renal biopsy and would therefore be a desirable alternative. If clinicopathological studies show that it is reliable for distinguishing between Alport's syndrome and thin basement membrane nephropathy, then it represents a good alternative.
Dr. Michaels: A renal biopsy may still be important when IgA nephropathy is in the differential diagnosis, which it often is.
Anatomical Diagnosis
Nephropathy with thin and focally disrupted glomerular basement membranes and decreased 3 and 5 chains of type IV collagen, consistent with a carrier state of X-linked Alport's syndrome.
Source Information
From the Renal Unit, Department of Medicine (D.J.R.S.), and the Department of Pathology (P.J.M.), Massachusetts General Hospital; and the Departments of Medicine (D.J.R.S.) and Pathology (P.J.M.), Harvard Medical School.
References
Ahmed Z, Lee J. Asymptomatic urinary abnormalities: hematuria and proteinuria. Med Clin North Am 1997;81:641-652.
McGregor DO, Lynn KL, Bailey RR, Robson RA, Gardner J. Clinical audit of the use of renal biopsy in the management of isolated microscopic hematuria. Clin Nephrol 1998;49:345-348.
Kohler H, Wandel E, Brunck B. Acanthocyturia -- a characteristic marker for glomerular bleeding. Kidney Int 1991;40:115-120.
Kitamoto Y, Tomita M, Akamine M, et al. Differentiation of hematuria using a uniquely shaped red cell. Nephron 1993;64:32-36.
Topham PS, Harper SJ, Furness PN, Harris KPG, Walls J, Feehally J. Glomerular disease as a cause of isolated microscopic haematuria. Q J Med 1994;87:329-335.
Donadio JV, Grande JP. IgA nephropathy. N Engl J Med 2002;347:738-748.
Gharavi AG, Yan Y, Scolari F, et al. IgA nephropathy, the most common cause of glomerulonephritis, is linked to 6q22-23. Nat Genet 2000;28:354-357.
Hudson BG, Tryggvason K, Sundaramoorthy M, Neilson EG. Alport's syndrome, Goodpasture's syndrome, and type IV collagen. N Engl J Med 2003;348:2543-2556.
Kashtan CE, Michael AF. Alport syndrome. Kidney Int 1996;50:1445-1463.
Savige J, Rana K, Tonna S, Buzza M, Dagher H, Wang YY. Thin basement membrane nephropathy. Kidney Int 2003;64:1169-1178.
Hebert LA, Betts JA, Sedmak DD, Cosio FG, Bay WH, Carlton S. Loin pain-hematuria syndrome associated with thin glomerular basement membrane disease and hemorrhage into renal tubules. Kidney Int 1996;49:168-173.
Tiebosch AT, Frederik PM, van Breda Vriesman PJ, et al. Thin-basement-membrane nephropathy in adults with persistent hematuria. N Engl J Med 1989;320:14-18.
Sakai K, Muramatsu M, Ogiwara H, et al. Living related kidney transplantation in a patient with autosomal-recessive Alport syndrome. Clin Transplant 2003;17:4-8.
Takemura T, Yanagida H, Yagi K, Moriwaki K, Okada M. Alport syndrome and benign familial hematuria (thin basement membrane disease) in two brothers of a family with hematuria. Clin Nephrol 2003;60:195-200.
Tanaka H, Kim ST, Takasugi M, Kuroiwa A. Isolated hematuria in adults: IgA nephropathy is a predominant cause of hematuria compared with thin glomerular basement membrane nephropathy. Am J Nephrol 1996;16:412-416.
Rumpelt HJ, Langer KH, Scharer K, et al. Split and extremely thin glomerular basement membranes in hereditary nephropathy (Alport's syndrome). Virchows Arch A Pathol Anat Histol 1974;364:225-233.
Piel CF, Biava CG, Goodman JR. Glomerular basement membrane attenuation in familial nephritis and "benign" hematuria. J Pediatr 1982;101:358-365.
Cohen RA, Brown RS. Microscopic hematuria. N Engl J Med 2003;348:2330-2338.
Rogers PW, Kurtzman NA, Bunn SM Jr, White MG. Familial benign essential hematuria. Arch Intern Med 1973;131:257-262.
Myers JC, Jones TA, Pohjolainen ER, et al. Molecular cloning of alpha 5(IV) collagen and assignment of the gene to the region of the X chromosome containing the Alport syndrome locus. Am J Hum Genet 1990;46:1024-1033.
Heidet L, Arrondel C, Forestier L, et al. Structure of the human type IV collagen gene COL4A3 and mutations in the autosomal Alport syndrome. J Am Soc Nephrol 2001;12:97-106.
Buzza M, Wilson D, Savige J. Segregation of hematuria in thin basement membrane disease with haplotypes at the loci for Alport syndrome. Kidney Int 2001;59:1670-1676.
Lajoie G. Approach to the diagnosis of thin basement membrane nephropathy in females with the use of antibodies to type IV collagen. Arch Pathol Lab Med 2001;125:631-636.
Liapis H, Gokden N, Hmiel P, Miner JH. Histopathology, ultrastructure and clinical phenotypes in thin glomerular basement membrane disease variants. Hum Pathol 2002;33:836-845.(David J.R. Steele, M.D., )
A 42-year-old woman visited the nephrology clinic for an evaluation of chronic microscopic hematuria.
Microscopic hematuria had been detected 14 years earlier during an episode of cystitis. She subsequently had several episodes of cystitis each year, but the hematuria persisted after treatment and resolution of the infections; usually there were 10 to 20 red cells per high-power field on examination of the urine, but occasionally more than 100, with findings of trace to 1+ proteinuria. An intravenous pyelogram obtained at the time of the initial diagnosis of hematuria was said to have shown a urethral stricture. Ten years before the current evaluation, a urologist prescribed daily nitrofurantoin to prevent recurrent urinary tract infections. A renal ultrasonographic examination prompted by the persistent microscopic hematuria showed normal-size kidneys, no hydronephrosis, and no evidence of renal stones. Cytologic examination of the urine showed no malignant cells.
Later that year, the patient's first pregnancy was complicated by gestational diabetes, which was controlled by diet, and by preeclampsia with a blood pressure of 150/95 mm Hg. Labor was induced, and the delivery was uncomplicated. A second pregnancy three years later was uncomplicated. Nine months after the second delivery, mild hypertension developed; systolic blood pressure ranged between 120 and 144 mm Hg and diastolic pressure ranged between 70 and 96 mm Hg over the next three years. Hematuria and intermittent proteinuria persisted. Another renal ultrasonogram was obtained and showed the right kidney to be 9.3 cm long and the left kidney to be 9.4 cm long without hydronephrosis. No residual fluid was seen within the urinary bladder after voiding. A nephrology consultation was requested.
The patient was a native of the Philippines and had emigrated to the United States at 26 years of age. She worked as a nurse. When she came to the nephrology clinic, she had not had an episode of cystitis for three years. A thyroidectomy for goiter was performed when she was 13 years of age, after which she was prescribed levothyroxine (0.125 mg per day). Her father had had hypertension and had died at the age of 72 from a stroke. Her mother was alive and had diabetes. Her brother died at 46 years of age while on dialysis, of renal failure that was reportedly caused by the use of analgesic agents for the treatment of chronic gout. Two sisters were said to have hematuria; one of them had hypertension, and the other a history of goiter. The patient's two daughters were well.
On physical examination, the patient's weight was 57.2 kg (126 lb), the blood pressure 138/88 mm Hg, and the pulse 72 beats per minute. The results of a physical examination were normal, except for scars from thyroid surgery. The results of a complete blood count, measurements of glucose and electrolyte levels, renal-function tests, measurement of serum immunoglobulin levels, protein electrophoresis, and tests for cryoglobulins, complement, antinuclear antibodies, rheumatoid factor, and urinary Bence Jones protein were normal. Serologic tests were positive for hepatitis B antibody, negative for hepatitis B antigen, and negative for hepatitis C antibodies. Urinalysis disclosed 20 to 50 red cells per high-power field and 1+ proteinuria. Microscopical examination of the urinary sediment disclosed dysmorphic red cells and two cellular casts thought to be red-cell casts. Treatment with lisinopril, 5 mg daily, was prescribed. A 24-hour urine collection of 1600 ml contained 1152 mg of creatinine and 160 mg of protein. At follow-up examinations, five weeks and eight weeks later, the blood pressure was 100/60 and 110/60 mm Hg, respectively.
A diagnostic procedure was performed.
Differential Diagnosis
Dr. David J.R. Steele: This patient presented to me in the clinic with long-standing microscopic hematuria, low-grade proteinuria, a history of mild hypertension, preserved renal function, and a family history of renal disease. Microscopic hematuria is generally defined as more than one to three red cells per high-power field in a centrifuged urine specimen. It has a broad differential diagnosis. In patients with hematuria without proteinuria, approximately 10 percent of cases are due to a glomerular process and the remaining cases are due to urologic factors, although estimates vary widely. In many cases, no cause is found despite extensive evaluation.1,2
Nonglomerular Causes of Microscopic Hematuria
Nonglomerular causes of microscopic hematuria involving the kidney and urinary tract include neoplasms of the kidney, the collecting system, the ureter, and the bladder; nephrolithiasis; cystic diseases; papillary necrosis; hypercalciuria; hyperuricosuria; and sickle cell disease. A urologic workup of this patient included a normal intravenous pyelogram and renal ultrasound imaging that showed kidneys that appeared normal and no evidence of a renal mass lesion. Cytologic examination of the urine was normal. Cystoscopy had not been performed, presumably because there were no risk factors for bladder cancer. Helical computed tomographic (CT) imaging either with or without contrast material — currently the imaging method of choice for diagnosing either a kidney stone or an occult cancer of the upper urinary tract, and more sensitive than ultrasonography — had not been done in this patient.
The crux of this patient's initial evaluation was the microscopical examination of the urine sediment. The sediment contained dysmorphic red cells and red-cell casts. These findings help us differentiate between hematuria arising from a glomerular source and hematuria from a nonglomerular source. Dysmorphic red cells, or acanthocytes, are red cells that have undergone microtrauma while traversing a diseased glomerular basement membrane; such trauma results in structural changes, including loss of biconvexity and the appearance of membrane blebs. Dysmorphic red cells are best seen during phase-contrast microscopical examination of a centrifuged urine sediment (Figure 1A and Figure 1B).
Figure 1. Dysmorphic Red Cells in Urinary Sediment.
Panel A shows red-cell casts (arrow) similar to the one seen in this patient. Panel B shows dysmorphic red cells (arrows), indicative of a glomerular lesion. (Photomicrographs from other patients, courtesy of Dirk Hentschel, Department of Nephrology, Massachusetts General Hospital.)
The reliability of dysmorphic red cells — on their own — as a predictor of glomerular disease in the absence of red-cell casts is controversial.3,4 However, the combination of dysmorphic red cells and red-cell casts is believed to pinpoint a glomerular origin of hematuria; this diagnosis is more likely to be valid if proteinuria is present. In this case, the level of proteinuria was below that which is ordinarily considered clinically significant (300 mg per 24-hour collection, or a protein-to-creatinine ratio of 0.3). Nevertheless, the combination of findings suggested hematuria of a glomerular origin.
Glomerular Causes of Microscopic Hematuria
Once the glomerulus has been defined as the source of hematuria, the differential diagnosis can be narrowed to a limited number of disease processes (Table 1). The probability that this patient had focal glomerulonephritis was small, because of her prolonged hematuria, the minimal proteinuria, her stable normal renal function, and the negative serologic workup. Her clinical presentation was not consistent with a collagen vascular process, anti–glomerular basement membrane disease, or vasculitis. Tests for hepatitis B surface antigen and hepatitis C antibody were negative. The long natural history in the absence of clinically significant proteinuria and hypertension is not consistent with poststreptococcal glomerulonephritis.
Table 1. Differential Diagnosis of Isolated Hematuria of Glomerular Origin.
The family history of renal disease suggested the possibility of a hereditary renal disorder. The patient had two sisters who had hematuria and apparently normal renal function; one is said to have had hypertension, although we do not have the details. In addition, her brother died at a young age of end-stage renal disease, with the cause said to be analgesics used to treat gout. We have incomplete records of these events, but we should consider alternative diagnoses, including the possibility that the brother had a hereditary renal disease. Hereditary renal diseases associated with hematuria include Alport's syndrome (hereditary nephritis), thin-basement-membrane nephropathy, polycystic kidney disease, Fabry's disease, the nail–patella syndrome, and possibly — in some kindreds — IgA nephropathy.
IgA Nephropathy
IgA nephropathy is a common cause of microscopic hematuria.5 It results from mesangial IgA deposition. Although some patients have an elevated IgA level, not all do; an increase in IgA level alone is not sufficient to produce this disease. A defect in galactosylation of IgA1 may play a role. A patient who has IgA nephropathy may present with hematuria (with or without proteinuria), hypertension, and a rising serum creatinine level. The natural history of the condition varies among patients, ranging from those who have hematuria with stable renal function to those (between 15 percent and 40 percent in reported studies) in whom end-stage renal disease develops. There are no markers that predict progressive disease in patients who present with only minor urinary abnormalities.6 A subgroup of patients with IgA nephropathy may have hereditary disease. A linkage of IgA nephropathy to chromosome 6q22–23 with a dominant mode of inheritance has been shown.7
Alport's Syndrome
Alport's syndrome is a rare hereditary renal disease caused by a defect in genes coding for the 5 chain of type IV collagen. The majority of cases are X-linked; autosomal recessive inheritance occurs in 5 percent of cases and autosomal dominant inheritance in a few kindreds. The first sign of the disease is microscopic or occasionally macroscopic hematuria. Alport's syndrome occurs predominantly in men, and affected male patients classically have hematuria, proteinuria (urinary protein excretion, less than 1 to 2 g per day), progressive renal failure, and sensorineural deafness. Lenticonus of the anterior lens capsule, retinopathy, and leiomyomatosis are sometimes associated with the disease. Deafness occurs in approximately 55 percent of patients. The urine sediment is likely to contain dysmorphic red cells and red-cell casts. Patients with Alport's syndrome lack a component of glomerular basement membrane, and anti–glomerular basement membrane glomerulonephritis may develop after kidney transplantation. The disorder is clinically variable, probably reflecting the complexity of collagen genetics.8,9
Heterozygous females in families with Alport's syndrome may have intermittent or persistent microscopic hematuria with no other manifestations of renal disease; about 10 percent of heterozygous female patients have no hematuria. Proteinuria is uncommon, as is hypertension. The prognosis for affected girls and women is generally good, but end-stage renal disease develops in some women. In such cases, gross hematuria in childhood, nephrotic-range proteinuria, and thickening of the glomerular basement membrane (identified by the use of electron microscopy) are associated with progressive nephritis. Hearing loss and lenticonus, although rare, are also associated with an adverse outcome in heterozygous female patients. Pregnancy does not appear to have an adverse effect on renal function in patients with mild disease but may accelerate the decline in renal function in those with severe disease.
Thin Basement Membrane Nephropathy
In thin basement membrane nephropathy, also known as benign familial hematuria or thin basement membrane disease, the glomerular basement membrane is uniformly thinned to about half its normal thickness. Many cases follow an autosomal dominant mode of inheritance and, as with Alport's syndrome, are caused by mutations in the type IV collagen gene — in this case the 3 and 4 chains. There is a female-to-male ratio of 1.6. The prevalence of this disease cannot be accurately estimated because of the reluctance of nephrologists to perform a renal biopsy in patients with isolated hematuria, but it is likely that thin basement membrane nephropathy occurs in about 1 percent of the general population.10 Patients present with hematuria; there may be proteinuria, although usually urinary protein excretion is less than 500 mg per day, and hypertension is rare. There are no extrarenal manifestations. Renal failure occurs rarely and, for unclear reasons, often in association with other glomerulonephritides. Focal segmental glomerulosclerosis is reported to occur in at least 5 percent of patients. IgA nephropathy may occur together with thin basement membrane nephropathy — probably more often than by chance alone.11 The diagnosis is based on the combination of hematuria and characteristic changes on renal biopsy and on the finding of hematuria in multiple family members without a history of end-stage renal disease. Treatment is nonspecific and includes control of hypertension, use of angiotensin-converting–enzyme inhibitors if proteinuria or hypertension is present, and modest dietary protein restriction.10,12
Differential Diagnosis of Alport's Syndrome and Thin Basement Membrane Nephropathy
The distinction between thin basement membrane nephropathy and Alport's syndrome is not always easy to make. It is important to distinguish between the two when possible, because of the different prognoses of these conditions and because of the implications for the offspring of the female carriers of Alport's syndrome. Since hearing loss, lenticonus, and retinopathy are found in fewer than 10 percent of female carriers of Alport's syndrome, thin basement membrane nephropathy and Alport's syndrome are difficult to distinguish on clinical grounds alone in women who have hematuria as their only clinical abnormality.13,14
The family history may be useful. A family history of hematuria without renal failure supports a diagnosis of thin basement membrane nephropathy. If the nature of renal failure in a family member is unknown, then information regarding hearing loss or eye disorders may be useful. In the case under discussion, there was no history of either in the brother who had end-stage renal disease. The absence of hearing loss or optical abnormalities, however, does not rule out Alport's syndrome as the cause of end-stage renal disease in his case, since these extrarenal abnormalities are not present in all cases. In questionable cases, a renal biopsy may be helpful.10,12,15,16,17
Role of Renal Biopsy
A renal biopsy is not routinely recommended in the evaluation of patients with isolated microscopic hematuria, unless there is evidence of clinically significant proteinuria or a progressive deterioration in renal function. In their review of microscopic hematuria in the Journal, Cohen and Brown18 recommended against performing a renal biopsy in cases of isolated glomerular microscopic hematuria, since available data suggest that identification of the specific disease does not make a difference in management or outcome. Complications of renal biopsy are infrequent but must be borne in mind. Major bleeding occurs in 1 to 2 percent of the patients who undergo biopsy, and mortality is about 0.1 percent. We accept that not having a tissue diagnosis is valid in most patients with isolated hematuria whose disease is following a benign course. In this case, however, I favored performing a biopsy because of increasing concern on the part of a medically sophisticated patient and our desire to define her underlying diagnosis in the context of her strong family history. The hope was that prognostic information would be obtained that would be reassuring to the patient and her family and that further evaluations could be avoided.
Dr. Nelson Goes (Nephrology): Does the fact that the patient comes from the Philippines alter the evaluation? Are there any tropical diseases that could cause chronic hematuria?
Dr. Steele: In tropical regions there is a high incidence of schistosomiasis, which may be manifested in the patient by lower urinary tract bleeding. It certainly is a consideration under appropriate circumstances.
Dr. David J.R. Steele's Diagnosis
Thin basement membrane nephropathy or X-linked Alport's syndrome or IgA nephropathy.
Pathological Discussion
Dr. Paul J. Michaels: The diagnostic procedure was a percutaneous renal biopsy. The glomeruli were normal when examined by light microscopy, except for focal, mild mesangial hypercellularity (Figure 2A). The interstitium, renal tubules, and vessels were normal. Immunofluorescent staining of the glomeruli showed slight segmental linear staining for IgG and albumin. Only very focal, trace granular staining for IgA and IgM was noted in the mesangium, excluding a diagnosis of IgA nephropathy. Electron-microscopical examination showed diffusely thin glomerular basement membranes (Figure 2B). Some segments were thickened, scalloped, and contained electron-dense granules ("microparticles"), but no definite laminations were seen (Figure 2C). Ultrastructural morphometric analysis revealed a harmonic mean (±SD) glomerular-basement-membrane thickness of 219±20 nm, with a range of 121 to 328 nm. The normal glomerular-basement-membrane thickness in women as measured by this method is 326±45 nm.
Figure 2. Examination of Renal-Biopsy Specimen by Light and Electron Microscopy.
The glomerulus shows a slight increase in the mesangial matrix, with focal mesangial hypercellularity (Panel A) (hematoxylin and eosin). On electron-microscopical examination, the glomerular basement membrane appears diffusely thin (Panel B). Focally, small electron-dense granules (microparticles) are present (arrowheads), and the endothelial portion of the basement membrane is scalloped (Panel C, arrows).
These histologic, immunofluorescent, and ultrastructural findings are consistent with a diagnosis of either thin basement membrane nephropathy or a carrier state of X-linked Alport's syndrome (Table 2). Thin glomerular capillary basement membranes are the only pathological abnormality in the kidneys of patients with thin basement membrane nephropathy.19 However, thin glomerular basement membranes are found in Alport's syndrome and may be the only finding in early Alport's syndrome and in female carriers of X-linked Alport's syndrome. In carriers of X-linked Alport's syndrome, however, there may also be areas of splitting and thickening of the basement membrane, which worsen over time; these abnormal areas are not seen in thin basement membrane nephropathy. In this case, the presence of widespread thin glomerular basement membranes in combination with focal membrane thickening, scalloping, and microparticles suggests that the patient is a carrier of X-linked Alport's syndrome. However, although full-blown Alport's syndrome is therefore excluded, the pathological findings alone are not sufficient to distinguish with certainty between thin basement membrane nephropathy and heterozygosity for an Alport mutation.
Table 2. Common Renal-Biopsy Findings in Conditions Causing Microscopic Hematuria.
The genetic mutations responsible for the phenotypic abnormalities seen in both X-linked and autosomal recessive or dominant Alport's syndrome and thin basement membrane nephropathy have been characterized (Table 3).20,21 These discoveries have enabled pathologists to use ancillary diagnostic techniques to narrow the differential diagnosis in patients with thin glomerular basement membranes. The three clinical entities have in common abnormalities in the chains of type IV collagen (COL4), specifically the 3, 4, and 5 chains, which form a triple helical protomer found in the glomerular basement membrane (Figure 3).8 X-linked Alport's syndrome is typically caused by mutations in the 5 chain of type IV collagen (COL4A5).20 In contrast, autosomal Alport's syndrome, which can be inherited in both a recessive and a dominant fashion, is the result of defects in the genes encoding for either the 3 (COL4A3) or the 4 (COL4A4) subunits of type IV collagen.21 The mutations seen in thin basement membrane nephropathy also frequently involve both the 3 and 4 chains of type IV collagen, suggesting that autosomal Alport's syndrome and thin basement membrane nephropathy may represent points on a spectrum of a single disease process.22 Thus, some persons with thin basement membrane nephropathy may have a single copy of a mutated gene in either the 3 or 4 chain of type IV collagen that, when present in a homozygous form, leads to autosomal recessive Alport's syndrome. Different mutations in these same genes occasionally lead to the less common autosomal dominant Alport's syndrome.
Table 3. Conditions Associated with Thin Basement Membrane on Electron Microscopy and Corresponding Mutations of Type IV Collagen.
Figure 3. Structure of the Chains of Type IV Collagen and Mutations in Renal Disease.
Six distinct chains (left) are arranged into three triple helical protomers composed of different chains (right). Each protomer has a 7S triple helical domain at the N-terminal; a long, triple helical, collagenous domain in the middle of the molecule; and a noncollagenous (NC1) trimer at the C-terminal. The 1, 1, 2 protomer is found in all basement membranes, whereas the 3, 4, 5 and 5, 5, 6 protomers are differentially distributed in various tissues (box). This heterogeneous distribution probably accounts for the variety of overlapping clinical syndromes associated with mutations in different chains. (The illustration has been adapted from Hudson et al.8)
The mutations in Alport's syndrome lead to a segmental reduction in the amount of both 3 and 5 collagen in the glomerular basement membrane; this defect can be detected by immunofluorescence staining with antibodies to these proteins. In contrast, the mutations in the 3 chain in thin basement membrane nephropathy do not produce this pattern. Segmental loss of glomerular staining for the 5 chain of type IV collagen suggests a carrier state for X-linked Alport's syndrome; however, normal staining does not necessarily rule out the diagnosis.23 Additional diagnostic tests include immunofluorescence staining of a skin-biopsy specimen for the 5 chain of type IV collagen. Interrupted staining in a female patient suggests a carrier status for X-linked Alport's syndrome, whereas even, linear staining supports the diagnosis of thin basement membrane nephropathy.24 Finally, sequencing of the gene for the 5 chain of type IV collagen can be performed to confirm or rule out X-linked Alport's syndrome, since this gene is usually unaffected in patients with thin basement membrane nephropathy.
In the patient under discussion, staining of the renal-biopsy specimen with antibodies to the 3 and 5 chains of type IV collagen revealed segmental reduction in the normal linear staining along the glomerular basement membranes for both proteins, as compared with a control glomerulus (Figure 4A and Figure 4B). This segmental reduction in staining for the 3 and 5 chains of type IV collagen further suggests a carrier state for X-linked Alport's syndrome.
Figure 4. Immunofluorescence Staining of Renal-Biopsy Specimens with Antibody for 3 Chains of Type IV Collagen.
Immunofluorescence staining of a specimen from a kidney without disease (Panel A) reveals bright, uninterrupted linear staining for the 3 chain of type IV collagen. However, staining of a specimen from the patient's glomerulus with the same monoclonal antibody reveals an overall decrease in staining intensity, with further segmental reduction of staining in the capillary loops (Panel B, arrows). A similar pattern was seen with the use of an antibody to the 5 chain.
Dr. Steele: Since her evaluation, the patient has been seen in annual follow-up visits. Two years after the diagnostic biopsy, she remains well, with no evidence of progressive renal disease. She continues to receive treatment for hypertension and has microscopic hematuria and stable mild proteinuria. She reports that her daughters have been tested and do not have hematuria. She is in the process of reviewing her diagnosis and its implications with other family members.
Dr. Lynn D. Cornell (Pathology): In the future, with a patient such as this one, would you consider doing a skin biopsy instead of a renal biopsy?
Dr. Steele: Skin biopsy is a much less invasive procedure than renal biopsy and would therefore be a desirable alternative. If clinicopathological studies show that it is reliable for distinguishing between Alport's syndrome and thin basement membrane nephropathy, then it represents a good alternative.
Dr. Michaels: A renal biopsy may still be important when IgA nephropathy is in the differential diagnosis, which it often is.
Anatomical Diagnosis
Nephropathy with thin and focally disrupted glomerular basement membranes and decreased 3 and 5 chains of type IV collagen, consistent with a carrier state of X-linked Alport's syndrome.
Source Information
From the Renal Unit, Department of Medicine (D.J.R.S.), and the Department of Pathology (P.J.M.), Massachusetts General Hospital; and the Departments of Medicine (D.J.R.S.) and Pathology (P.J.M.), Harvard Medical School.
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