Abstract: Objective: To analyze the correlation between nail involvement and ultrasound changes in the distal interphalangeal joint in patients with psoriasis. Methods: Patients with moderate to severe psoriasis vulgaris (PsO) and psoriatic arthritis (PsA) were enrolled, and their basic clinical data, characteristics of nail damage, nail unit and distal interphalangeal joint changes under ultrasound were recorded. Results: A total of 38 patients with moderate to severe PsO and 35 patients with PsA were included. The incidence of nail changes in PsA group was higher than that in moderate to severe PsO group (85.7% vs 63.2%, P=0.028), mNAPSI score in PsA group (P=0.042) and deck thickness (P<0.001) were also higher than that in PsO group. Compared with moderate to severe PsO group, PsA group had a higher detection rate of enthesopathy and osteophyte formation (77.1% vs 28.9%, P<0.001; 74.3% vs 31.6%, P<0.001). In the fingers of patients with moderate to severe PsO, the incidence of extensor tendon enthesopathy and joint effusion was higher in the nail involvement group than in the fingers without nail involvement group (11.4% vs 2.6%, P<0.001;35.6% vs 12.6%, P<0.001). The incidence of finger extensor tendon enthesopathy, joint effusion, synovitis, bone erosion and osteophyte formation in PsA patients with nail involvement group was higher than that without nail involvement group (Ps<0.05). On the same finger, the mNAPSI score, onycholysis and pitting were related to extensor tendon enthesopathy in all patients, especially the pitting with strong correlation. (OR 2.02; 95%CI 1.13-3.60). Conclusion: Patients with PsA are more prone to nail involvement and enthesopathy at distal interphalangeal joint. The occurrence of extensor tendon enthesopathy is significantly related to mNAPSI score, onycholysis and pitting.

Key words: psoriasis, nail involvement, musculoskeletal ultrasound, joint changes, enthesopathy