Psoriatic nail dystrophy is associated with erosive disease in the distal interphalangeal joints in psoriatic arthritis: a retrospective cohort study

Objective To assess if the association between psoriatic nail dystrophy and radiographic damage in the hands of patients with psoriatic arthritis (PsA) is specific to the distal interphalangeal joints. Methods A convenience sample of patients were collated from the Bath longitudinal PsA cohort. All patients had PsA according to the CASPAR criteria, scored radiographs of their hands, and documented nail scores as measured by the Psoriatic Nail Severity Score (PNSS). Chi-square tests were performed to examine for association between features of nail dystrophy and radiographic damage in the distal interphalangeal joints (DIPjs), and proximal interphalangeal or metacarpophalangeal joints (non-DIPjs) of the corresponding digits. Results 134 patients were included, with a median age of 53 (IQR 44, 61) years and disease duration of 7 (IQR 3, 15) years. The presence of any form of psoriatic nail dystrophy was associated with erosion at the DIPjs of the corresponding digit (OR 1.9; 95% CI 1.23, 2.83; p Conclusion The presence of psoriatic nail dystrophy, particularly onycholysis, is associated with erosive disease at the DIPjs. Subungal hyperkeratosis is more strongly associated with erosive damage at the DIPjs than non-DIPjs. These findings support the anatomical and pathological link between nail and DIP joint disease.