Background The autoimmune myopathies (IM) comprise a broad spectrum of acquired muscular disorders characterized by autoimmune damage of skeletal muscle and complex visceral involvement, leading to chronic dysfunction and disability.

Objectives The aim of our study was to assess the association between Raynaud's phenomenon (RP) and capillaroscopic findings in patients with polymyositis (PM), dermatomyositis (DM) and anti-synthetasic syndrome (ASS), and to identify possible correlation with clinical and serological pattern.

Methods Nailfold videocapillaroscopy (Optilia 200x) was performed in a cohort of 27 patients diagnosed with IM, 12 with RP and 15 age-, sex-, and disease-duration-matched without RP, and 19 healthy controls. Total number of capillaries, enlarged and giant capillaries, ramified capillaries, haemorrhages, haemosyderin deposits were each scored by a semiquantitative assessment, while the disorganization of the vascular array and avascular area were scored as present/absent.

Data about IM activity (Myositis Disease Activity Assessment Tool), severity (Myositis Damage Index) and physical function (Stanford HAQ) were also collected.

Findings were analysed using linear and logistic regression, adjusted for age and sex (SPSS-19 software).

Results Patients with IM were frequently abnormal, with significant lower capillary density, higher dimensions, enlarged capillaries, haemorrhages and haemosyderin deposits as compared with healthy controls (p<0.001).

80% of cases reported RP as the first manifestation of their disease, with frequently nailfold capillary abnormalities as compared to non-RP patients (p<0.01). Enlarged capillaries (p<0.01), avascular areas (p<0.05) and capillary hemorrhages (p<0.05) were typically described in DM and most of ASS patients, but not in PM without RP.

In addition, a scleroderma-like capillaroscopy pattern was identified in RP-positive patients, either DM or ASS. On the other hand, either normal or nonspecific capillaroscopy findings were found in RP-negative and PM.

Pulmonary involvement (p<0.01) and arthritis/arthralgia (p<0.01) were significantly more common in ASS with RP, especially in those who developped RP years before myositis, while digestive (proximal dysphagia) manifestations (p<0.01) were more common in DM with RP, particularly in those with late-onset RP.

We found an association between the presence of either active or late scleroderma pattern, elevated serum CK and disease activity: capillary loss was significantly associated high muscle and global disease activity, as well (p<0.05).

Anti-Jo-1 and anti-PL12 antibodies were associated with reduced capillary density (p<0.05), whereas anti-SRPs associated with reduced capillary density, enlarged capillaries and hemorrhages (p<0.05).

Conclusions RP is associated with particular capillaroscopic findings in different IM subsets, suggesting that prognostic relevance of RP in myositis should be evaluated.

Significant changes in the capillary pattern reported in IM, particulary reduced density, size abnormalities, haemorrhages, indicating that nailfold videocapillaroscopy may be useful as an outcome measure of microvascular disease in IM

Disclosure of Interest None declared