Abstract
A 13-year-old girl of atypical juvenile myasthenia gravis (MG) who presented mainly with generalized muscle atrophy, bulbar signs and joint contracture was reported. She had not almost presented generalized muscle weakness and ptosis.
Her chief complaints on admission were marked emaciation and persistent moist cough. She was noted to have unclear pronounciation three years prior to admission. Moist cough lasted all day long for the past 10 months. Rarely she developed double vision and ptosis. On admission, she was markedly emaciated (body weight 28kg) with diffuse muscle atrophy including the tongue muscle. Severe emaciation was thought to be due to bulbar signs such as difficulty in swallowing. Her muscle strength was almost within normal limits except for neck flexor muscles. Muscle fatigability was not induced by repetitive exercises such as eye blink and hand-grip tests. Extra-ocular movements on upper and lateral gazes were limited moderately without definite ptosis. Joint contracture which was due to neurogenic muscle atrophy was present in her upper vertebrae. Her chin did not touch to the chest on neck flexion. There was mild scoliosis of vertebral column. Tensilon test did not show constant results. Muscle biopsy demonstrated mild neurogenic changes scattered small angulated fibers, mild variation in fiber size and an increased number of type 2C fibers. We estimated that diffuse muscle atrophy was due to neurogenic change. The anti-acetylcholine receptor (ACh-R) antibody titer was increased to 2.66 pmoles/ml. Prednisolone therapy (80mg every other day) for two weeks resulted in a complete recovery from ophthalmoplegia and a rapid decrease in the anti-ACh-R antibody titer to the normal range.
Joint contracture caused by neurogenic muscle atrophy are not reported by now in a generalized form of childhood MG. In spite of reduced muscle bulk there were no definite muscle weakness and muscle fatigability. These symptoms were atypical in childhood MG. Although the prognosis of our case was at first thought to be poor because of her muscle atrophy and bulbar signs, a good response to prednisolone therapy was against our initial estimation.
