Incidence and characteristics of Myasthenia gravis in Dar Es Salaam, Tanzania.

Objective: To ascertain the annual incidence and characterise the clinical features of Myasthenia gravis in Dar es Salaam, Tanzania during a ten-year period from 1st January 1988 to 31 December 1998.

Design: Prospective cumulative registration at a major urban hospital of all patients with newly diagnosed Myasthenia gravis who were resident in Dar es salaam.

Setting: Muhimbili Medical Centre Teaching Hospital, Dar es Salaam, Tanzania.

Subjects: Forty seven patients, twenty males, twenty seven females satisfied the criteria for the diagnosis of Myasthenia gravis (MG).

Results: The annual incidence of MG of both sexes was 3 per 1,000,000 population of all age groups (95% CI 2.0 to 3.6). The incidence per 1,000,000 population was lowest in those aged below ten years 2.2 (95% CI 1.4 to 3.4) which was statistically significant. The incidence per 1,000,000 per year was higher in females but this was not statistically significant. The clinical presentation of MG in Tanzania was localised disease accounting for 47% ocular type and 53% was mild to moderately severe generalised type MG. Twenty per cent of patients with generalised MG presented with bulbar features. Single fibre electromyography was the most sensitive test.

Conclusion: Myasthenia gravis is fairly rare in Tanzania as is in other sub-Saharan countries and presents in similar way to European in terms of age, sex, and clinical features. Ocular Myasthenia gravis was more prevalent in Tanzania than in Europe.