Patients with progressive pseudorheumatoid dysplasia: from clinical diagnosis to molecular studies

Progressive pseudorheumatoid dysplasia (PPD) is a rare inherited autosomal recessive disease for which no prevalent data have been reported in China. We aimed to identify PPD based on clinical manifestations and imaging analysis of the bony skeleton and then to investigate gene mutations of Wnt1-inducible signaling pathway protein 3 (WISP3) in Chinese patients with PPD. Seven patients (aged 9-49 years) from six unrelated Chinese families all presented with a waddling gait, progressive swelling and restricted joint movements, and all were diagnosed as having PPD according to clinical signs and symptoms, as well as radiographic imaging. The radiographic imaging revealed no erosive arthropathy, but showed platyspondyly, irregular or wedged/ovoid anterior end-plates of the vertebral bodies, coxa vara and widened epiphyses or metaphyses including the femoral head and the metacarpophalangeal and interphalangeal joints. Normal laboratory values were found for the erythrocyte sedimentation rate, C-reactive protein and rheumatoid factors in all patients. Molecular studies revealed that five patients carried c.624_625insA/c.729_735delGAGAAAA, c.624_625insA/c.866_867insA, c.866_867 insA/c.866_867insA, Q46X/C114W and C223G/C114W mutations, respectively. In conclusion, our findings suggest that in order to avoid misdiagnosis, physicians should carefully examine the entire skeleton, including the spine, in addition to the skeletal extremities. Mutation analysis of the WISP3 gene is useful for confirming the clinical and radiographic diagnosis of PPD.