Introduction and objectives: The nail unit is a subject of interest in several diseases, often involving different medical fields. Even if few data are available for psoriasis and psoriatic arthritis, no data regarding ultrasonography and imaging are present for other degenerative and inflammatory conditions. The aim of this study was to explore through imaging the changes of nail and enthesis in inflammatory and degenerative conditions in order to find qualitative and quantitative changes related to distal interphalangeal joints.
Methods: The study sample was composed of 51 patients affected by psoriatic arthritis, 31 affected by psoriasis, 37 subjects with rheumatoid arthritis, 34 with osteoarthritis and 50 healthy controls for a total of 203 individuals. Ultrasonography of the nails was performed after clinical evaluation in a cross-sectional study design by blinded ultrasonographers who were blind to patient data. Data about power Doppler signal of the nail bed, tendon entheses, thickness of nail plate and nail bed were recorded.
Results: Patients affected by psoriasis and psoriatic arthritis differ from other subgroups, and power Doppler signal at the enthesis seems to be an exclusive feature of psoriatic arthritis (Pearson's chi-square of 5297 and p < 0.001 with adjusted residuals). Nail plate thickness also differs in psoriasis and psoriatic arthritis, but surprisingly in osteoarthritis, too, with similar results.
Conclusions: This study provides qualitative and quantitative data regarding the ultrasonographic features of nails in several rheumatic diseases with a potential role of ultrasonography in characterising them.
Keywords: Nail bed; Nail plate; Psoriasis; Psoriatic arthritis; Ultrasonography.