Ultrasound entheseal abnormalities at the distal interphalangeal joints and clinical nail involvement in patients with psoriasis and psoriatic arthritis, supporting the nail-enthesitis theory.

OBJECTIVE: It has been shown that nail involvement in psoriasis is associated with systemic enthesopathy. Our objective was to evaluate the association of nail involvement and enthesopathy at distal interphalangeal joint (DIP) level in psoriasis (PsO) and psoriatic arthritis (PsA) patients.

METHODS: Consecutive patients (54 PsO and 56 PsA) seen at the outpatients clinic in this cross-sectional study were included. All patients underwent both clinical and ultrasound (US) assessment on the same day.

RESULTS: US revealed enthesopathy in at least 1 DIP joint in 9 patients with PsO (17%, 95% CI: 8-29%) and in 18 patients with PsA (32%, 95% CI: 20-46%). US extensor tendon enthesopathy was detected in a higher proportion of fingers with clinical nail involvement compared with fingers without clinical nail involvement, both in PsO and PsA patients (61.2% vs 16.8%, p < 0.0001 and 60.1% vs 22%, p < 0.0001, respectively). Among patients with PsO, 20% (95% CI: 7-41%) and 14% (95% CI: 4-32%) of those with and without clinical nail involvement showed enthesopathy on US examination, respectively (p = 0.54). Among PsA patients, the prevalence of enthesopathy was 30% (95% CI: 15-49%) for patients with clinical nail involvement and 35% (95% CI: 17-56%) for those without nail involvement (p = 0.71).

CONCLUSION: Nail disease was associated with DIP US enthesopathy. There was a significant increased prevalence of extensor tendon enthesopathy in fingers with involved nails both in PsO and PsA, although no association was found between nail involvement and extensor tendon enthesopathy at patients' level. These features might support the nail-entheseal pathogenesis theory at DIP level.