Ultrasonography of the nail unit reveals quantitative and qualitative alterations in patients with psoriasis and psoriatic arthritis

Aims: The nail unit is a matter of interest both for dermatologist and rheumatologist. The nail is considered one of the possible targets of assessment, especially when ultrasonography is performed. The aim of the study is to highlight peculiar features and alterations of the nail unit in patients affected by psoriasis and psoriatic arthritis versus healthy controls using ultrasonography. Materials and methods: The study sample included 82 patients affected by psoriasis and/or psoriatic arthritis and 50 healthy controls. The patients were consecutively enrolled during their routine visit in the outpatient clinic and they performed clinical and ultrasonographic evaluation of the nail. The evaluation of disease activity was done using Disease Activity in Psoriatic Arthritis (DAPSA), Psoriasis Activity Severity Index (PASI), and Nail Psoriasi Severity Index (NAPSI). Results: Multivariate analysis of variance was performed between groups. Post hoc analysis underlined the differences between healthy and affected regarding nail plate thickness (0.063±0.011 cm for patients with psoriasis, 0.065±0.014 cm for patients with psoriatic arthritis and 0.051±0.006 cm for healthy controls, p<0.05). Elementary lesions of nail plate and nail bed were compared using Pearson’s chi square test between patients in psoriasis and psoriatic arthritis groups, with no differences except for a trend for onycholisis and crumbling (p=0.07 and 0.06, respectively) in the psoriatic arthritis group. ROC curves were calculated (AUC = 0.68) obtaining also quantitative cut offs for nail plate and nail bed thickness in the affected vs healthy patients. Conclusions: Our study shows that ultrasonography may be a potential advantage in clinical practice. Our results strengthen the information already available in the literature and add quantitative parameters for ultrasonography of the nail.