PO:24:057 | Qualitative and quantitative analysis of nailfold videocapillaroscopy in patients with idiopathic inflammatory myopathies: focus on muscle histology

Jacopo Landro¹, Marius Cadar¹, Davide Mohammad Reza Beigi^1|2, Ilaria Bisconti¹, Francesca Romana Di Ciommo¹, Elena Platania¹, Martina Salerno¹, Beatrice De Girolamo¹, Annalisa Villa¹, Angelica Gattamelata¹, Simona Truglia¹, Cristiano Alessandri¹, Fabrizio Conti¹, Valeria Riccieri¹. | ¹Policlinico Umberto I, Roma, Italy; ²Clinica Reumatologica Madonna dello Scoglio, Cotronei, Italy.

Background. Idiopathic inflammatory myopathies (IIM) are a group of autoimmune diseases characterized by inflammation of the muscle with clinical manifestations such as skin rash, interstitial lung disease, heart involvement or arthritis. Within IIM, we distinguish dermatomyositis (DM), immune-mediated necrotizing myopathy (IMNM), anti-synthetase syndrome (ASyS), inclusion body myositis (IBM), and Polymyositis (PM). Nailfold video-capillaroscopy (NVC) is a useful technique to study microvascular abnormalities in autoimmune diseases and a scleroderma-like (SL) pattern has been reported in about 70% of DM patients and in 35% of those with ASyS. Histologically, muscular findings are shared across IIM subgroups, such as sarcolemmal expression of MHC I and inflammatory infiltrates. Others are more specific: perifascicular atrophy (PFA) in DM or perifascicular necrosis (PFN) in ASyS. The aim of our study was to evaluate qualitatively and quantitatively the capillaroscopic alterations in IIM patients, for their possible associations with histological data.

Materials and Methods. Patients with IIM who underwent muscle biopsy and NVC were prospectively enrolled. Morphological parameters were assessed qualitatively (number, length, distribution, and size of capillary loops, as well as microhemorrhages and neoangiogenesis). We also assigned a semiquantitative score (0–3) and other quantitative scores (total megacapillary count, mean of megacapillaries apex width, mean capillary density, number of hemorrhages, and mean of avascular areas).

Results. We enrolled 20 patients including 9 with DM, 4 with ASyS, and 7 with PM. Table 1 presents the main clinical, histological, and capillaroscopic features of our cohort. Regarding capillaroscopic findings, we observed a significant association between the presence of a SL pattern and DM diagnosis (p=0.0098). Comparing the biopsies regardless of the type of idiopathic inflammatory myopathy (IIM), we observed a higher mean semiquantitative score in patients exhibiting perifascicular fiber hypotrophy compared to those without (mean 2, IQR 0–2 vs mean 0, IQR 0–1;p=0.0359), as well as a significant association with the presence of an SL pattern (p=0.0246). This group of patients also showed a marked reduction in capillary density (p=0.0190) and an increased mean number of avascular areas (p=0.0058). ASyS patients displayed a significant association with perifascicular necrosis (p=0.0010), consistent with previous reports, but also with perifascicular fiber hypotrophy (p=0.0260), whereas we did not confirm the described association with DM.

Conclusions. To our knowledge, this study is the first to explore the relationship between NVC findings and muscle biopsy features in IIM patients using both qualitative and quantitative methods. Our data suggest a link between perifascicular muscle fiber hypotrophy—where muscle vasculature damage is believed to originate—and specific capillaroscopic abnormalities in DM and ASyS cases. Expanding our understanding of the underlying peripheral vasculopathy in the different forms of IIM requires a larger patient cohort and a deeper histological evaluation of muscular and vascular injury.