Background/Purpose: A third of cases of skin psoriasis are complicated by potentially incapacitating psoriatic arthritis (PsA). Nail psoriasis, especially onycholysis, is present in more than 70% of PsA and the risk of developing PsA is significantly higher in patients with nail involvement (OR = 2.24; 95% CI [1.26-3.98]) (Wilson FC. Arthritis Rheumatism 2009). In this study, we wanted to test the hypothesis that onycholysis, in patients without PsA, may be a potential clinical marker of subclinical distal pathogenic enthesopathy and thus may present early bone microstructural alterations of the distal interphalangeal joint.

Methods: We compared bone microstructural damages (erosions, osteophytes) of the distal interphalangeal joint using High Resolution Peripheral Quantitative Computed Tomography imaging HR-pQCT (XtremCT Scanco, Switzerland®) in patients with psoriatic onycholysis without PsA (ONY) and in patients with cutaneous psoriasis only without PsA or nail psoriasis (PsO). We used, as reference for bone features, patients with peripheral psoriatic arthritis (PsA) and healthy gender/age-matched controls. Ultrasonography of the target distal interphalangeal joint was used to assess enthesopathy (finger extensor tendon thickness), synovitis, and nail apparatus (nail plate and matrix).

Results: Between 2013 and 2016, 80 patients were recruited in the four following groups (20 per group): controls, ONY, PsO and PsA. Mean±SD age of the participants was 45.7±4.3 years. Nail plate thickness, matrix and finger extensor tendon thickness were increased in ONY versus PsO patients. Erosions and synovitis were observed in respectively 8.3% and 4.1% of ONY patients but never in PsO patients. By HR-pQCT, ONY patients were associated with a mean number of 3.6±0.77 erosions of the distal interphalangeal joint versus only 0.21±0.1 in PsO patients (p=0.035). PsA patients presented several V-shaped, Omega-shaped, U-shaped erosions and osteophytes.

Conclusion: We describe for the first time the existence of bone erosions in interphalangeal distal joints of patients with psoriatic onycholysis. These findings support the pathogenic role of enthesopathy in joint involvement of PsA. These data underly the potential severity of onycholysis compared to isolated cutaneous psoriasis only. Onycholysis may be considered as a clinical marker for patients with psoriasis who have an increased risk of joint destruction.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/distal-interphalangeal-joint-erosions-assessed-by-hr-pqct-in-patients-with-psoriatic-onycholysis/