Limb girdle myasthenia: a study of familial and sporadic cases.

Chronic limb girdle myasthenia gravis (MG) is a rare entity. We describe six such patients (F:M 4:2) who constituted 5% of 120 MG cases in a seven year study. The disease was familial in four and sporadic in two. No patient had ocular muscle weakness either at presentation (mean of 18.2 months after onset of illness) or during a mean follow up period of 36 months. Diagnosis was established by a positive decremental response on repetitive stimulation of a proximal muscle. Muscle biopsy was essentially normal in all five patients. All patients responded to acetylcholinesterase inhibitors, although to varying degrees. Four patients also received steroids. One patient with sporadic MG had transient worsening but others showed partial improvement. It is noteworthy that the initial diagnosis in these patient was other than MG. Diagnosis of limb girdle myasthenia needs to have a strong index of suspicion as it has therapeutic implications.