Epidemiology of polymyositis-dermatomyositis in Israel, 1960-76.

We attempted to identify all cases with polymyositis and/or dermatomyositis (PM-DM) admitted to hospitals in Israel during 1960-76. The diagnosis of PM-DM was retrospectively confirmed in 86 Jewish patients. The age-adjusted incidence rates increased from 1.30 in 1960-64 to 2.57 in 1970-74, with an overall incidence of 2.18 new cases diagnosed annually per 10(6) population. The male:female ratio in this series was 0.59. Females predominated among patients younger than 60 years of age, while males and females aged 60 or more appeared to be equally affected. The age distribution was heterogeneous with modes in the second and seventh decades. The annual incidence of PM-DM increased from 0.47 cases per 10(6) persons in the third decade to a peak of 6.32 in the seventh. The incidence of childhood PM-DM among non-Western Jews(of African or Asian origin) was significantly higher than that among Western Jews (of European or American origin). On the other hand, the incidence of adult PM-DM among Western Jews exceeded that among Jews of non-Western extraction.