Nailfold videocapillaroscopy in juvenile dermatomyositis: detailed correlations between microvascular abnormalities with clinical and laboratory parameters from an observational retrospective single-center study.

Introduction: Juvenile dermatomyositis (jDM) is a systemic autoimmune disease mainly affecting the skeletal muscle and skin. The aim of our study was to investigate the possible correlations between nailfold videocapillaroscopy (NVC) findings with clinical and laboratory parameters in patients with jDM.

Methods: Twenty-eight jDM patients (mean age 7.1 ± 3 years, mean disease duration 3.1 ± 3 years), evaluated between 2019 and 2023, classified according to Bohan and Peter criteria, were age- and sex-matched with healthy controls. Clinical, laboratory, and NVC parameters were collected at first visit and after 1 year again in a subgroup of patients (n = 9).

Results: Positivity for myositis-specific autoantibodies (MSA) was associated with a lower mean capillary density (p = 0.02) in jDM patients. Additionally, the presence of giant capillaries was significantly more frequent in MSA-positive patients (p = 0.04). The skin component of the disease activity score (VAS and DAS skin score) showed a significant inverse correlation with capillary density (r = -0.53, p = 0.007) and was significantly higher in patients with giant capillaries (median 5.5 vs 1, p = 0.005). Periungual telangiectasias and Gottron's papules were significantly associated with a reduction of the mean capillary count and with the presence of giant capillaries (all p-values < 0.05). Interestingly, no significant changes in NVC parameters were reported after 1 year of receiving immunosuppressive treatment.

Conclusions: Capillary loss and the presence of giant capillaries at NVC analysis were significantly associated with clinical and laboratory markers of skin disease activity in jDM. These findings suggest that NVC may serve as a promising non-invasive tool to support disease assessment, although further prospective studies are needed to confirm its role in clinical practice. Key Points • Nailfold videocapillaroscopy (NVC) abnormalities, particularly capillary loss and giant capillaries, correlate significantly with skin disease activity in juvenile dermatomyositis (jDM). • Myositis-specific antibodies (MSA), especially anti-TIF1γ, are associated with more severe microvascular damage, suggesting their potential role in patient stratification. • NVC parameters remained stable over 1 year of immunosuppressive treatment, highlighting the need for longer-term studies to evaluate microvascular change progressions in jDM. • NVC may represent a promising non-invasive biomarker to support the clinical assessment and follow-up of patients with jDM, but further validation in larger prospective studies is warranted.