Nailfold capillary microscopy in polymyositis and dermatomyositis.

Nailfold capillary microscopy was performed in 19 patients with polymyositis (PM) and 16 with dermatomyositis (DM). Enlarged capillary loops were seen more frequently in patients with DM (56%) than in those with PM (21%). Avascular lesions occurred in both PM and DM, but were more prevalent and more severe in patients with DM. Raynaud's phenomenon, arthritis, and pulmonary involvement were associated with greater numbers of enlarged capillary loops and more severe avascular lesions. The severity of the observed microvascular abnormalities did not correlate with the occurrence of malignancy or active myositis, but appeared to lessen with prolonged disease remission.