Progressive pseudorheumatoid dysplasia

Progressive pseudorheumatoid dysplasia (PPD), also known as progressive pseudorheumatoid arthropathy of childhood (PPAC) or spondyloepiphyseal dysplasia tarda with progressive arthropathy, is a rare inherited skeletal disorder caused by mutations in the WISP3 (also known as CCN6) gene. Despite its name suggesting a rheumatologic condition, PPD is a bone and cartilage disorder that primarily affects the joints and spine. It is often misdiagnosed as juvenile idiopathic arthritis because of its clinical presentation, but importantly, it lacks the inflammatory markers typically seen in true rheumatic diseases. The condition usually becomes apparent in early childhood, typically between ages 3 and 8, with progressive joint stiffness, swelling (particularly of the interphalangeal joints of the hands), and restricted range of motion. Over time, patients develop progressive involvement of large and small joints, including the hips, knees, and spine. Spinal changes include platyspondyly (flattened vertebral bodies) and progressive kyphosis or lordosis. The epiphyses of long bones become enlarged and irregular on radiographs. Affected individuals often experience significant pain and progressive loss of mobility, and many require joint replacement surgery by early adulthood. Short stature may develop due to spinal involvement. There is currently no disease-specific or curative treatment for progressive pseudorheumatoid dysplasia. Management is supportive and symptomatic, focusing on pain control, physical therapy to maintain joint mobility, and orthopedic interventions including joint replacement surgery when necessary. Anti-inflammatory and immunosuppressive medications used for rheumatoid arthritis are ineffective because the disease is not driven by inflammation. Early and accurate diagnosis is important to avoid unnecessary immunosuppressive therapy and to guide appropriate orthopedic management.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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