Inflammatory myopathies (IM) are a group of muscle diseases occurring both in children and adults. Nailfold videocapillaroscopy (NVC) alterations are described in IM, but available data are discordant, including differences between polymyositis (PM) and dermatomyositis (DM). The aim of this study was to describe the capillaroscopic differences between PM and DM patients and possible correlation with clinical and serological features. We analyzed 52 unselected patients with IM in a cross-sectional study in a 6-month period. NVC findings of 29 DM and 23 PM patients were compared with those of 52 patients with primary Raynaud’s phenomenon. Tortuosities, capillary loss, enlarged and giant capillaries, microhemorrhages, and ramified capillaries were scored by a semiquantitative rating; disorganization of the vascular array, avascular areas, and scleroderma pattern were scored as presence/absence. Sex, mean age, and mean disease duration were similar in both groups. Disorganization of the vascular array, enlarged and giant capillaries, capillary loss, and scleroderma-like pattern were observed almost only in IM patients. Significant differences were observed between PM and DM with higher frequency and mean score of NVC changes in DM. In DM patients with disease duration ≤6 months (14/29 patients), capillary density was significantly reduced (P = 0.039) and giant capillaries more frequent (P = 0.027), compared with patients with longer disease duration, while a scleroderma pattern tended to be more frequent in patients with a disease duration of less than 6 months. On the contrary, no differences were observed for ramified capillaries with regard to disease duration. Capillaroscopic alterations are identified only in DM patients as expression of diffuse microangiopathy; surprisingly, more severe changes were associated with shorter disease duration, while persistence of ramified capillaries with long-standing disease.
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