The association between nailfold capillary density and pulmonary and cardiac involvement in medium-to long-standing juvenile dermatomyositis

Objective To explore the associations between microvascular abnormalities as assessed by nailfold capillaroscopy (NFC) and pulmonary and cardiac involvement in patients with juvenile dermatomyositis (DM) who are assessed after medium‐ to long‐term follow‐up. Methods Fifty‐eight patients with juvenile DM were examined a mean ± SD of 17.0 ± 10.6 years after symptom onset. Nailfold capillary density (NCD) and a neovascular pattern (defined as an active or late scleroderma pattern) were analyzed, with blinding to clinical data. Pulmonary involvement was assessed by pulmonary function tests including spirometry, diffusing capacity for carbon monoxide (DLco ), and body plethysmography. High‐resolution computed tomography (HRCT) was also performed. Cardiac involvement was assessed by electrocardiography, Holter monitoring (heart rate variability), and echocardiography. Results Patients with low NCD (<6 capillaries/mm) (n = 21), compared to patients with normal NCD (≥6 capillaries/mm) (n = 37) had lower forced vital capacity (89.7% versus 98.5% predicted), total lung capacity (87.8% versus 94.5% predicted), and more often had low DLco values (15 [71%] of 21 patients versus 14 [38%] of 37 controls) (all P < 0.05). Use of HRCT to assess airway disease was more frequent in the group with low NCD (6 [30%] of 20 patients versus 3 [8%] of 36 patients in the normal NCD group; P = 0.034). No associations between NCD and cardiac parameters or between neovascular pattern and pulmonary or cardiac parameters were observed. Conclusion In patients with juvenile DM, low NCD was associated with lung involvement, which was mostly subclinical. No significant associations with cardiac involvement were observed. These results shed light on possible mechanisms underlying organ involvement, but further and preferably larger studies are needed to identify NCD as a potential biomarker for lung and cardiac involvement in juvenile DM