Patients with juvenile dermatomyositis (DM) and low nailfold capillary density (NCD) have impaired pulmonary function test (PFT) results and more frequent high-resolution computed tomography (HRCT) abnormalities compared with patients with normal NCD, according to the results of a cohort study published in Arthritis Care & Research.

The investigators sought to examine the associations between microvascular abnormalities evaluated by nailfold capillaroscopy, and pulmonary and cardiac involvement, in patients with juvenile DM who were assessed after medium- to long-term follow-up. A total of 58 patients with juvenile DM were evaluated at a mean of 17.0 ± 10.6 years after onset of symptoms. NCD and neovascular pattern, defined as active or late scleroderma pattern, were analyzed and blinded to clinical data. Pulmonary involvement was evaluated by PFTs, including spirometry, body plethysmography, and diffusion capacity for carbon monoxide (DLCO). HRCT was also performed. Electrocardiography, echocardiography, and Holter monitoring were used to evaluate cardiac involvement.

Overall, 21 patients with low NCD (<6 capillaries/mm), compared with 37 patients with normal NCD (≥6 capillaries/mm), presented with lower forced vital capacity (89.7% vs 98.5%, respectively), lower total lung capacity (87.8% vs 94.5%, respectively), and lower DLCO (71% vs 38%, respectively; P< .05 for all measurements).

HRCT-assessed airway disease was reported more often in the low NCD group compared with the group with normal NCD (30% vs 8%, respectively; P =.034). There were no associations observed between NCD and cardiac parameters, nor between neovascular pattern and pulmonary or cardiac parameters.

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The investigators concluded that the lung involvement reported among patients with juvenile DM and low NCD was mainly subclinical in nature. Although these study results suggest that systemic microvascular remodeling might be an underlying mechanism for pulmonary involvement in these patients, additional, preferably larger, studies are warranted to identify NCD as a potential biomarker for organ involvement in patients with juvenile DM.

Reference

Barth Z, Schwartz T, Flatø B, et al. The association between nailfold capillary density and pulmonary and cardiac involvement in medium- to long-standing juvenile dermatomyositis [published online June 28, 2018]. Arthritis Care Res (Hoboken). doi: 10.1002/acr.23687