Enthesopathy in patients with nail psoriasis - a cross-sectional evaluation of clinical, onychoscopic and ultrasonographic features.

Background Nail involvement in psoriasis is common and may be an indicator not only of disease severity, but also of the presence of psoriatic arthritis. However, the relationship of nail psoriasis with enthesitis remains under-explored. Aims This study was conducted to evaluate the clinical, onychoscopic (nail dermatoscopic) and ultrasonographic features in patients with nail psoriasis. Materials and Methods All nails of twenty adult patients with nail psoriasis were examined clinically and onychoscopically. Patients were evaluated for psoriatic arthritis (Classification Criteria for Psoriatic Arthritis), the severity of cutaneous disease (Psoriasis Area Severity Index) and nail disease (Nail Psoriasis Severity Index). Ultrasonography of the clinically involved digits was performed for evidence of distal interphalangeal joint enthesitis. Results Out of 20 patients, 18 patients had cutaneous psoriasis and 2 had isolated nail involvement. Among the 18 patients with skin psoriasis, 4 had associated psoriatic arthritis. The most commonly observed clinical and onychoscopic features were pitting (31.2% and 42.2%), onycholysis (36% and 36.5%) and subungual hyperkeratosis (30.2% and 30.5%), respectively. Ultrasonographic evidence of distal interphalangeal joint enthesitis was seen in 57% (175/307) of the digits with clinical nail involvement. Enthesitis was more common in patients with psoriatic arthritis (77% vs 50.6%). Nail thickening, crumbling and onychorrhexis (all features of nail matrix involvement) were significantly associated with enthesitis (P < 0.005). Limitation The major limitation was the small sample size and lack of controls. Only the clinically involved digits were evaluated for enthesitis. Conclusion Enthesitis was frequently detected on ultrasonography in patients with nail psoriasis, even in clinically asymptomatic individuals. Nail features of thickening, crumbling and onychorrhexis may predict underlying enthesitis and the potential development of arthritis. A comprehensive evaluation could help identify patients with psoriasis at risk for arthritis, helping improve long-term outcomes.