Progressive Pseudorheumatoid Dysplasia Misdiagnosed as Juvenile Idiopathic Arthritis: Advanced Joint Destruction.

Progressive pseudorheumatoid dysplasia (PPRD) is a rare autosomal recessive arthropathy often misdiagnosed as juvenile idiopathic arthritis (JIA). We present the case of a 52-year-old woman with polyarthralgia since age 7, initially diagnosed with seronegative polyarticular JIA and treated with methotrexate at doses ranging from 10 to 15 mg weekly for over two decades, despite the absence of clinical improvement. The rationale for prolonged use was the persistence of joint symptoms under the initial diagnosis of JIA, leading clinicians to continue disease-modifying therapy. Clinical examination revealed joint deformities, limited range of motion, short stature, and limb length discrepancy. Radiographs showed characteristic PPRD features, including flattening of the metacarpophalangeal joints, brachymetatarsia, vertebral fractures, and lumbar osteopenia. Pelvic imaging demonstrated bilateral hip prostheses with loosening of the right prosthesis, superior migration of the femoral component, and screw fracture. Laboratory tests revealed normal inflammatory markers and negative rheumatoid factor and anti-cyclic citrullinated peptide (anti-CCP) antibodies. This case highlights the diagnostic challenges of PPRD and the potential for irreversible joint destruction when diagnosis is delayed. Clinicians should suspect PPRD in early onset polyarthritis with non-inflammatory joint involvement and negative immunologic tests to avoid unnecessary immunosuppressive therapy and initiate timely supportive management.