Is myasthenia gravis more benign in the Indian population?
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1 Departments of Neurology, Little Flower Hospital and Research Centre, Angamaly, Kerala, India
2 Departments of Ophthalmology, Little Flower Hospital and Research Centre, Angamaly, Kerala, India
The paper authored by Panda et al stimulated our curiosity.[1] We were especially intrigued by two patients (No: 2 and 5) who had ocular myasthenia with thymoma and remained in MGFA Class I for five and three years respectively before going into crisis. This goes against two grains of conventional wisdom that a) ocular myasthenia tends usually not to generalize after three years and b) the course of patients with thymoma is aggressive with frequent crises. There is no inviolable tenet in medicine and the first aphorism derives from a study of natural history which found generalized myasthenia developing in less than 6% if weakness remained confined to ocular muscles in the first three years.[2] The serological status of these patients and the nature and grade of thymoma would be of interest. We would like to know whether the institutional protocol included pre-thymectomy plasmapheresis.
The paper suffers a few flaws that plague retrospective studies. Since the point of entry was through ward admission, patients with Classes I and IIa who may conceivably have been treated as outpatients in the Neurology or Ophthalmology departments would be excluded. Hence the proportion of myasthenics developing crisis could well be even lower than the 9.69% computed. This is significantly less than expected but corresponds with the conclusions of a study of ocular myasthenia from our institution.[3] No myasthenic crisis was encountered in 48 patients who had presented in MGFA Class I. The follow up period was over five years in 5 and 3 years in 20 patients. Despite the logical hypothesis advanced by the authors that infections and drug default could trigger frequent crises in developing countries our impression is that ocular onset myasthenia behaves less aggressively in our subjects. The alternative explanation would be that the incidence of crisis is overstated in most neurological series because of the greater proportion of severely affected patients.
Bulbar involvement may hasten respiratory compromise because of pooling of secretions. However, bulbar involvement is almost universal during myasthenic crisis and often heralds crisis rather than instigates it. Only 2 of the 11 patients were reported to have bulbar involvement when previously classified and it would be incorrect to infer from this data that bulbar presentation confers higher risk of crisis.
Minor criticisms apart, the investigators deserve congratulation and more needs to be studied about this disease that exhibits ethnically diverse behavior.
References
1. Panda S, Goyal V, Behari M, Singh S, Srivastava T. Myasthenic crisis: A retrospective study. Neurol India 2004;52:453-6.
2. Grob D, Arsura E, Brunner N, Namba T. The course of myasthenia gravis and therapies affecting outcome. Ann NY Acad Sci 1987;505:472-99.
3. Gopinath D. Ocular Myasthenia - A Clinical Study. DNB Ophthalmol Thesis 2004.(Menon A, Madhukar M, Sree)
2 Departments of Ophthalmology, Little Flower Hospital and Research Centre, Angamaly, Kerala, India
The paper authored by Panda et al stimulated our curiosity.[1] We were especially intrigued by two patients (No: 2 and 5) who had ocular myasthenia with thymoma and remained in MGFA Class I for five and three years respectively before going into crisis. This goes against two grains of conventional wisdom that a) ocular myasthenia tends usually not to generalize after three years and b) the course of patients with thymoma is aggressive with frequent crises. There is no inviolable tenet in medicine and the first aphorism derives from a study of natural history which found generalized myasthenia developing in less than 6% if weakness remained confined to ocular muscles in the first three years.[2] The serological status of these patients and the nature and grade of thymoma would be of interest. We would like to know whether the institutional protocol included pre-thymectomy plasmapheresis.
The paper suffers a few flaws that plague retrospective studies. Since the point of entry was through ward admission, patients with Classes I and IIa who may conceivably have been treated as outpatients in the Neurology or Ophthalmology departments would be excluded. Hence the proportion of myasthenics developing crisis could well be even lower than the 9.69% computed. This is significantly less than expected but corresponds with the conclusions of a study of ocular myasthenia from our institution.[3] No myasthenic crisis was encountered in 48 patients who had presented in MGFA Class I. The follow up period was over five years in 5 and 3 years in 20 patients. Despite the logical hypothesis advanced by the authors that infections and drug default could trigger frequent crises in developing countries our impression is that ocular onset myasthenia behaves less aggressively in our subjects. The alternative explanation would be that the incidence of crisis is overstated in most neurological series because of the greater proportion of severely affected patients.
Bulbar involvement may hasten respiratory compromise because of pooling of secretions. However, bulbar involvement is almost universal during myasthenic crisis and often heralds crisis rather than instigates it. Only 2 of the 11 patients were reported to have bulbar involvement when previously classified and it would be incorrect to infer from this data that bulbar presentation confers higher risk of crisis.
Minor criticisms apart, the investigators deserve congratulation and more needs to be studied about this disease that exhibits ethnically diverse behavior.
References
1. Panda S, Goyal V, Behari M, Singh S, Srivastava T. Myasthenic crisis: A retrospective study. Neurol India 2004;52:453-6.
2. Grob D, Arsura E, Brunner N, Namba T. The course of myasthenia gravis and therapies affecting outcome. Ann NY Acad Sci 1987;505:472-99.
3. Gopinath D. Ocular Myasthenia - A Clinical Study. DNB Ophthalmol Thesis 2004.(Menon A, Madhukar M, Sree)