Progressive pseudorheumatoid dysplasia is an inherited skeletal dysplasia with autosomal recessive transmission. Radiographs of the spine show abnormalities similar to those seen in spondyloepiphyseal dysplasia tarda. The clinical presentation, but not the imaging study findings, suggest juvenile idiopathic arthritis. We report 3 cases of progressive pseudorheumatoid dysplasia in the same family.

A 4-year-old girl had been receiving follow-up for 3 years for seronegative, polyarticular juvenile idiopathic arthritis progressing by flares and remissions. The disease was unresponsive to anti-inflammatory medications. Findings at admission included inflammatory joint pain, joint swelling, range-of-motion limitation, and joint deformities in the hands, wrists, ankles, and knees. The hips were normal. Normal values were found for the erythrocyte sedimentation rate and C-reactive protein level. Synovial fluid removed from one of the knees exhibited mechanical properties. Plain radiographs of the hands and forefeet showed no evidence of joint destruction. Bilateral hip dysplasia was noted on a radiograph of the pelvis. The diagnosis of juvenile idiopathic arthritis was reconsidered. A study of the family identified two similar cases, in a brother and paternal uncle. The brother, who was 14 years old, had similar manifestations without laboratory evidence of inflammation; radiographs disclosed dysplasia of the hips and metacarpophalangeal epiphyses. Manifestations in a paternal uncle consisted of spinal stiffness, thoracic kyphosis, and motion-range limitation at the hips; radiographs showed normal sacroiliac joints and bilateral hip dysplasia. A diagnosis of progressive pseudorheumatoid dysplasia with polyarticular involvement was given.

Progressive pseudorheumatoid dysplasia is an autosomal recessive disease characterized by abnormal cartilage homeostasis. It should be included among the differential diagnoses of juvenile idiopathic arthritis.