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

OBJECTIVE
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.


METHODS
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.


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 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.


CONCLUSION
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.