[Isolated proximal muscular weakness disclosing myasthenic syndrome]

Three cases of chronic limb-girdle myasthenia gravis (one man and two women) are reported. The duration of the disease was three, five and 20 years respectively. None had oculobulbar weakness during this period nor fluctuating symptoms. The primary diagnosis was myopathy in two cases and myelopathy in the other one. In view of this diagnosis, several features were atypical: absence of marked wasting, preservation of tendon reflexes and normal serum creatine kinase activity. Finally, diagnosis of myasthenia gravis was established by the occurrence of a characteristic decremental muscular response to repetitive stimulation and by positive edrophonium test. It seems that the rate of positivity of acetylcholine receptor antibody is lower than in the common form of the disease. Two patients responded to acetylcholinesterase inhibitors and one to high-doses intravenous human immunoglobulins. These and previous cases described in the literature raise the problem of the definition of an unusual form of myasthenia gravis or of a new type of neuromuscular disease characterized by the presence of distinctive changes on muscular biopsies, specially tubular aggregates as in one of our cases. However, this unusual form of chronic limb-girdle weakness has to be recognized because treatments are effective in most cases.