Ultrasound nail imaging on patients with psoriasis and psoriatic arthritis compared with rheumatoid arthritis and control subjects.

OBJECTIVE: The objective of this study was too show findings at finger nails level revealed by high-frequency gray-scale ultrasound (US) and power Doppler in patients with psoriatic arthritis (PsA),and cutaneous psoriasis compared with rheumatoid arthritis and control subjects.
METHODS: We studied 35 patients with PsA, 20 with cutaneous psoriasis, and control groups (28 control subjects and 27 patients with rheumatoid arthritis). All nails of both hands were observed (1097 nails, 3 excluded because of trauma). In every patient, we classified the morphologic abnormalities disclosed in ventral and dorsal nail plates. We also measured the distance between ventral plate and the bone margin of the distal phalanx at the right index finger.
RESULTS: All patients and control subjects presented abnormalities in the US imaging. Those with psoriatic arthritis and cutaneous psoriasis showed a higher number of compromised nails. When classifying those abnormalities using the typology of Wortsman et al, patients with psoriatic arthritis showed loosening of the borders of the ventral plate (type II), whereas patients with cutaneous psoriasis showed focal hyperechoic involvement of the ventral plate without involvement of the dorsal plate (type I). Patients of the control group could not be classified, although 31 of 55 showed thinning of the ventral plate without hyperechoic deposits. Nineteen of 35 patients with psoriatic arthritis, and 10 of 20 patients with cutaneous psoriasis did not show any nail clinical alterations. Nevertheless, the US detected type II alterations in the first group and type I in the second group. Patients with psoriatic arthropathy had power Doppler increases in distal interphalangeal joints and nail beds in a statistically significant form (P = 0.0001).When measuring the distance between the ventral plate and the bone margin of the distal phalanx, there was homogeneity among samples in patients and control subjects. A receiver operating characteristic curve analysis determined that a cut point of 2 mm clearly defined these 2 groups. There was a significant difference (P < 0.0001) between the mean distance ventral plate-osseous margin of the distal phalanx in psoriatic arthritis patients (P = 0.001) and patients with cutaneous psoriasis (P = 0.005) versus rheumatoid arthritis patients (P = 0.548).
CONCLUSIONS: As a predominant finding in our study, we observed abnormalities of the ventral plate in patients with PsA (type II) and abnormalities (type I) in patients with cutaneous psoriasis. We found a significant difference between the mean distance ventral plate-osseous margin of the distal phalanx in patients with PsA and patients with cutaneous psoriasis versus control subjects. Ultrasound imaging could be a feasible and sensitive tool to describe, measure, and follow morphologic characteristics and changes of the nail in psoriatic and/ or psoriatic arthritis patients with or without clinical nail lesions.