Features of polymyositis and dermatomyositis in the elderly: A case-control study

Objective Polymyositis (PM) and dermatomyositis (DM) are uncommon idiopathic inflamma tory myopathies (IIM). Little is known about these diseases in the elderly. We attempted to define the characteristics of PM/DM in the elderly by a ca se-control study involving the retrospective review of medical files of PM/ DM patients. Methods We drew from among 200 PM/DM patients being followed in our Internal Medici ne Department 21 patients (14F / 7M), aged greater than or equal to 65 year s at the onset of myositis (17 PM / 4 DM) (mean: 69.9 +/- 4.8 yrs.). They w ere compared with 21 (15F / 6M) randomly selected younger patients with IIM : PM (14) and DM (7) (mean: 46.4 +/- 12.4 yrs). Clinical, biological, elect rophysiological and pathologic features, treatment regimens and side-effect s in the 2 groups were collected. Results Clinical features were similar for the 2 groups. Elderly patients tended to have a higher frequency of cancer (24% vs 9.5%, p = 0.06), particularly of rectal adenocarcinoma. The time from disease onset to diagnosis was signif icantly longer in older patients (26 +/- 37 months vs 9 +/- 15 months; p = 0.02), normal CK levels were more frequent (40% vs 5%; p = 0.02) and serum CK levels were lower than for the population as the whole (11.5 N vs 22 N, p < 0.03). Electromyography features were more frequently suggestive of a c hronic form of the disease in elderly patients. Treatment regimens and shor t-term side-effects were similar for the 2 groups. Conclusion PM and DM are often diagnosed late in the elderly. Biological data and elec tromyography features argue for a chronic form of the disease in this age g roup. Clinical and endoscopic rectal examinations should be carried out in elderly patients with PM/DM.