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

Polymyositis (PM) and dermatomyositis (DM) are uncommon idiopathic inflammatory 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 case-control study involving the retrospective review of medical files of PM/DM patients.

We drew from among 200 PM/DM patients being followed in our Internal Medicine Department 21 patients (14 F/7 M), aged > or = 65 years at the onset of myositis (17 PM/4 DM) (mean: 69.9 +/- 4.8 yrs.). They were compared with 21 (15 F/6 M) randomly selected younger patients with IIM: PM (14) and DM (7) (mean: 46.4 +/- 12.4 yrs). Clinical, biological, electrophysiological and pathologic features, treatment regimens and side-effects in the 2 groups were collected.

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 significantly 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 chronic form of the disease in elderly patients. Treatment regimens and short-term side-effects were similar for the 2 groups.

PM and DM are often diagnosed late in the elderly. Biological data and electromyography features argue for a chronic form of the disease in this age group. Clinical and endoscopic rectal examinations should be carried out in elderly patients with PM/DM.