Background and aims Nailfold capillaroscopy (NVC) is an useful, non-invasive, reproducible and cost-effective favourable diagnostic tool able to assess the shape of capillaries in the periungal region and the presence of their peculiar abnormalities, essential in the differential diagnosis of connective tissue diseases (CTD).

Methods The aim of the study was to evaluate if selected NVC pictures are linked to SLE onset in a cohort of 42 CTD-affected women presenting Raynaud’s phenomenon, observed over 36 months. All of them were examined by this method every 6 months. We considered the following NVC parameters: presence of ectasic capillary loops (diameter ≥20 µm); megacapillaries (≥50 µm); hemosiderin deposits; capillary number reduction; neo-angiogenesis phenomena; micro-vascular array disorganisation. CTD and SLE diagnoses were posed according to the 2015 ACR/SLICC criteria. Qualitative variables were expressed in frequencies; their association, by non-parametric tests. Quantitative variables were assessed by analysis of co-variance.

Results The presence of hemosiderin deposits, ectasic loops and neo-angiogenic phenomena was strongly associated to the clinical subgroup of patients that later developed SLE (12/42 subjects; OR=13.5). The variable meandering deposits was the more strongly associated to SLE onset (OR=8.32; p<0.0101). The independent variables ectasic loops (OR=12.16) and neo-angiogenic phenomena (OR=6.60) were predictive for the persistence of CTD diagnosis.

Conclusions Nailfold capillaroscopy, summarising, can help in CTD management, since the presence of typical capillaroscopic abnormalities seems to be related to the development of SLE.