A late infantile case of myasthenia gravis (MG) with anti-muscle-specific receptor tyrosine kinase (MuSK) high antibody (Ab) titer is reported from Kyushu University, Fukuoka; and Nagasaki University, Japan. The onset with bilateral ptosis and abnormal phonation occurred after febrile seizures at 2 years of age. The diagnosis by a positive edrophonium test at age 3 years was followed by treatment with oral prednisolone. Ocular symptoms responded but bulbar symptoms persisted and worsened by age 12 years. The addition of pyridostigmine and increase in dose of steroid had limited benefit. Thymectomy was performed at age 26 years, with no response. On admission at age 29, he had marked facial weakness, nasal voice and dysphagia, and choked on drinking water. The tongue was atrophic with a triple-furrowed appearance, and the neck and proximal muscles of extremities were weak, without fasciculations. Tendon reflexes and sensation were normal. Edrophonium infusion improved speech and swallowing. Anti-MuSK Ab measured by radioimmunoassay was 4.80 nmol/L (normal, <0.05). His voice, swallowing and muscle strength improved after plasma exchange using Spectra. 
COMMENT. The authors cite reports of anti-MuSK MG mainly in middle-aged female adults, and a frequency of anti-MuSK Ab in AChR seronegative MG in 38% to 47% of cases. The present late infantile case suggests a wider spectrum of disease. The response to immunotherapies was thought to rule out a diagnosis of congenital MG.
A study of 77 juvenile myasthenia gravis patients, evaluated over a period of 34 years at the National Institute of Mental Health, Bangalore, India, and compared to 290 patients with MG onset after 15 years of age, showed 30% had ocular myasthenia and the remainder had generalized MG at onset . MG was familial in 10 (13%), with siblings affected. Treatment with corticosteroids was used in 52 (67%), and 5 received azathioprine in addition. Thymectomy was performed in 11, thymic histology showing hyperplasia in 8 and thymoma in 1. In 64 patients with follow-up information (mean 6.2 years; range 6 mos to 25 yrs), 10 (18.5%) had complete remission for at least one year without therapy, 25 (39%) were asymptomatic, 28 (44%) were partially improved, and 9 (14%) where unchanged or worse. Two died, and 4 had crises.