Myasthenia Gravis : Clinical Spectrum And Long Term Follow-Up Study

Abstract

Data from 386 patients, fairly representative of myasthenic population seeking medical advice, were analyzed for clinical spectrum, course and long-term outcome. There were 237 males and 149 females (3:2) with a mean age at onset of 30.6 years. Family history of myasthenia was noted in 5.4% patients. During the first month after the onset symptoms and signs were confined to ocular muscles in 47%, bulbar muscles in 12.5% and involved extremities in 9.4% of patients while 30% individuals had generalized MG. Fifteen patients had chronic limb girdle myasthenia. Of the 181 patients with ocular myasthenia at onset, 53% patients subsequently developed generalized disease and in 44% of these patients it occurred after two years of the onset. Thymectomy was performed in 16% of patients and 70% of the patients were treated with one or more immunosuppressive drugs at sometime. At last follow-up (mean -5.1 yrs), 41 % patients were asymptomatic, 40% reported improvement and 19% deteriorated. Drug free stable remission was achieved in 11% of patients. There was a trend for better outcome in patients undergoing thymectomy than medically treated patients, however the drug free remission rate was same in both the groups. MG was lethal in 11% of patients, principally in women, older than 35 years, and in patients in grade 3 or worse at first observation. Forty-three episodes of myasthenic crisis in 34 patients were analyzed. Infection was the commonest precipitating event. Median interval between the onset of symptoms to crisis was 13 months. Nine episodes of crisis were fatal, with a mortality rate of 21%. A significant reduction in crisis mortality from 40% during 1980-1990 to 10.2% during 1991 to 1999 was noted, reflecting improvement in management strategies.