Systematical analysis of nine Chinese patients with progressive pseudorheumatoid dysplasia and assessment of calcitriol treatment
Authors: Yin Lei , Mao Youying , Zhou Yunfang , Shen yongnian , Chen Huijin , Zhou Wei , Jin Yanliang , Huang Hua , Yu Yongguo , Wang Jian 
Published: June 2020

Abstract
Background: Progressive pseudorheumatoid dysplasia (PPRD) (MIM 208230) is a rare genetic disease characterized by progressive noninflammatory arthropathy affecting primarily the articular cartilage. Most patients are initially misdiagnosed because of the rarity of the disease and lack of awareness by most clinicians. Therefore, the purpose of the present study was to provide further diagnostic options to help clinicians make early precise diagnosis, and to investigate a new potential treatment for patients with PPRD. Methods: Clinical manifestations, radiographic features, Sanger Sequencing to determine WISP3 gene mutation and follow-up records were collected in 9 Chinese patients with PPRD. The time until diagnosis, relationship between clinical phenotypes and genotypes, and treatment effects were analyzed. Results: The clinical history and characteristics, mutations in the WISP3 gene, radiological data, treatment and outcome of 9 PPRD children were collected and reviewed. There were 3 pairs of siblings in this group and one patient had parental consanguinity. Five patients were misdiagnosed with juvenile idiopathic arthritis (JIA). The onset of disease in most patients (8/9) was between 3 and 6 years of age. The interval between onset of symptoms and obtaining the diagnosis for 8 of the patients varied between 3.6 years to 20 years. The onset of symptoms included enlarged and stiff interphalangeal joints of the fingers, gait disturbance or joint pain. Blood analysis revealed normal range of inflammatory parameters (erythrocyte sedimentation rate, C-reactive protein). Serum levels of 25-hydroxyvitamin D3 were analyzed in six patients and ranged from 6.16 to 22.1ng/ml, all lower than the normal range. Radiographic findings included different degree of abnormal vertebral bodies, epiphyseal enlargement of the interphalangeal joints with juxta-articular osteopenia, or reduction in hip articular space and cyst-like structures femoral head. A total of 7 variants in the WISP3 gene were identified in the 9 cases, presenting with three homozygous variants (c.397_404delCAAGTGTT, c.667T>G, and c.589+2T>C) and three compound heterozygous variants (c.589+2T>C/c.667T>G, c.624dupA/c.756C>A, and c.646T>C/c.1000T>C). After the treatment of calcitriol in the 6 patients with low level of 25-hydroxyvitamin D3 for 1.25 years to 1.75 years, two cases showed stable clinical disease activity and the other four patients joints’ pain and abnormal gait had improved. Conclusions: Combining the patient’s family history, clinical features presenting with abnormal gait or enlarged and stiff interphalangeal joints of the fingers, normal inflammatory markers, and the characteristic radiographic findings, we can obtain the clinical diagnosis of PPRD for the patients at a very early stage of the disease. The patients with PPRD having c.624dupA mutation in WISP3 may have delayed onset. Calcitriol showed treatment benefit by improving symptoms and decelerating progression of PPRD disease.