Psoriatic Arthritis Mutilans: Characteristics and Natural Radiographic History.

Objective: (1) To compare clinical characteristics of patients with psoriatic arthritis (PsA) with PsA mutilans (PAM) and without PAM, and (2) to determine the rate of PAM radiographic progression.

Methods: A retrospective cohort study was conducted of all patients with PsA attending a teaching hospital. The most recent hand and feet radiographs were screened for PAM. Serial radiographs (earliest to most recent) were quantitatively scored for osteolysis, erosion, joint space narrowing, and osteoproliferation.

Results: Out of the 610 cases, 36 PsA cases had PAM (5.9%). PAM cases were younger at diagnosis of PsA than non-PAM cases (p = 0.04), had more prevalent psoriatic nail dystrophy (OR 5.43, p < 0.001), and worse health assessment questionnaire score (1.25 vs 0.63, p < 0.04). Radiographic axial disease (OR 2.31, adjusted p = 0.03) and especially radiographic sacroiliitis (OR 2.99, adjusted p = 0.01) were more prevalent in PAM. PAM were more likely than non-PAM cases to have used a disease-modifying antirheumatic drug (DMARD; OR 16.36, p < 0.001). Out of 33 cases, 29 PAM cases had initiated a synthetic DMARD and 4/13 had initiated anti-tumor necrosis factor (anti-TNF) prior to first demonstration of PAM. A median 5 radiographs were scored for each PAM case (interquartile range 3-7). PAM progressed from monoarticular (60%) to polyarticular (80%) involvement. Osteolysis was initially rapid and progressive in the hands and feet, tapering later during disease course. Nail dystrophy predicted more severe osteolysis (p = 0.03).

Conclusion: Compared with non-PAM cases, PAM cases have earlier age at PsA diagnosis, poorer function, more prevalent nail dystrophy, and more radiographic axial disease/sacroiliitis. The rate of osteolysis is higher in earlier disease, and more severe in those with nail dystrophy. DMARD and anti-TNF therapy appear not to prevent PAM occurrence.