The hand and wrist are among the most common anatomical areas involved in rheumatic diseases, especially seropositive and seronegative rheumatoid arthritis (RA) and psoriatic arthritis (PsA). The purpose of this study was to identify the most differentiating radiographic characteristics of PsA, seropositive RA, and seronegative RA, particularly in the early stages. A retrospective analysis of radiographic hand findings was performed on 180 seropositive RA patients (29 males, 151 females, mean age at the point of acquisition of the analyzed radiograph of 53.4 y/o, SD 12.6), 154 PsA patients (45 males, 109 females, age median of 48.1 y/o, SD 12.4), and 36 seronegative RA patients (4 males, 32 females, age median of 53.1 y/o, SD 17.1) acquired during the period 2005-2020. Posterior-anterior and Nørgaard views were analyzed in all patients. The radiographs were evaluated for three radiographic findings: type of symmetry (asymmetric/bilateral/changes in corresponding joint compartments/'mirror-image' symmetry), anatomic location (e.g., wrist, metacarpophalangeal (MCP), proximal interphalangeal (PIP), distal interphalangeal (DIP) joints), and type of lesions (e.g., juxta-articular osteoporosis, bone cysts, erosions, proliferative bone changes). The study showed that symmetric distribution of lesions defined as 'lesions present in corresponding compartments' was more suggestive of seropositive or seronegative RA than PsA. Lesions affecting the PIP joints, wrist, or styloid process of the radius; juxta-articular osteoporosis, joint space narrowing, joint subluxations, or dislocations were more common in patients with seropositive RA than in those with PsA, whereas DIP joints' involvement and proliferative bone changes were more likely to suggest PsA than seropositive RA. Lesions in PIP, MCP, and wrist joints, as well as erosions, advanced bone damage, joint subluxations, dislocations, and joint space narrowing, were more common in seropositive RA patients than in seronegative RA patients. The ulnar styloid was more commonly affected in seronegative RA patients than in PsA patients. The study confirmed that types of bone lesions and their distribution in the hands and wrists can be useful in differentiating seropositive RA from PsA and suggests that seronegative RA varies in radiological presentation from seropositive RA and PsA.
Keywords: hand radiograph; psoriatic arthritis; rheumatoid hand; seronegative rheumatoid arthritis; seropositive rheumatoid arthritis.