[Progressive pseudorheumatoid dysplasia misdiagnosed as ankylosing spondylitis: a case report]

In this study, we reported a case of progressive pseudorheumatoid dysplasia in Peking University Third Hospital. A 56-year-old male patient presented with hip joint pain for more than 40 years and multiple joints pain with limitation of movements of these joints for 28 years. This patient suffered from joint pain and impaired range of motion of the hip, knee, elbow and shoulder gradually, associated with difficulty in walking and inability to take care of himself. He was diagnosed with "femoral head necrosis" or "ankylosing spondylitis" in local hospitals, but the treatment of nonsteroidal antiinflammatory drugs (NSAIDs) and sulfasalazine was not effective. Up to the age of 14, the patient displayed normal physical development, with the highest height was about 158 cm, according to the patient recall. However, his height was 153 cm at present. There was no history of similar illness in any family member. Physical examinations descried limitation of movement of almost all joints. Enlargement and flexion deformity of the proximal interphalangeal (PIP) joints of the hands resulted in the claw hand appearance. Limited abduction and internal and external rotation of the shoulder and hip could be find. He had normal laboratory findings for blood routine test, biochemical indexes and acute phase reactants such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). Furthermore, HLA-B27 and autoimmune antibodies such as rheumatoid factor (RF), anti-cyclic citrullinated peptide (anti-CCP) antibody and antinuclear antibody (ANA) were all negative. X-ray of the hip showed loss of the joint space and irregularities of the femoral head, both femoral head were flattened, it could be see hyperplasia, osteophytes, bilateral femoral neck thicken, neck dry angle turned smaller. The radiological findings of the spinal vertebra indicated kyphosis deformity, narrowing of the intervertebral discs, vertebral syndesmophytes and flattening of the vertebra. However, there was no clues of bone marrow edema in the lumbar MRI. At last, genetic testing for the Wnt1-inducible signaling pathway protein 3 (WISP3) gene was done and indicated compound heterozygous mutations: 756C>G and c.866dupA. These two mutations were derived from the patient's mother and father (the patient's parents each had a heterozygous mutation). Two exons of the WISP3 gene had nucleotide changes leading to amino acid mutations. According to the patient's history, symptoms, physical examinations, radiological findings and genetic testing, the final definitive diagnosis was progressive pseudorheumatic dysplasia.