The influence of race, sex, and puberty on incidence, severity, and outcome of juvenile myasthenia gravis beginning before age 20 years was evaluated in 115 patients seen at the University of Virginia, Duke University, and University of North Carolina at Chapel Hill. White patients with prepubertal disease onset had an equal sex ratio, and female predominance increased during and after puberty. Males had less severe disease than females. Black patients showed a constant F:M ratio of 2:1 in all pubertal-onset groups. Spontaneous remissions only occurred in white patients with prepubertal onset; and persistent symptoms for more than 10 years were least frequent in this group. Early thymectomy in white patients was followed by more remissions and milder symptoms than late thymectomy. Black patients had infrequent remissions, and similar disease severity after early or late thymectomy. 
COMMENT. This study documents the importance of race, sex, and puberty on the incidence, severity, response to thymectomy, and outcome in juvenile myasthenia gravis. Thymectomy was most effective in white patients when performed within 1 year of peripubertal disease onset. See Progress in Pediatric Neurology II, Chicago, PNB Publ, August 1994, for further reports of juvenile myasthenia gravis from the University of Iowa, a multicenter study in Italy, and from the Mass General Hospital, Boston.