Specific early signs and long-term follow-up findings of progressive pseudorheumatoid dysplasia (PPRD) in the Turkish cohort

Progressive pseudorheumatoid dysplasia (PPRD) is a spondyloepiphyseal dysplasia caused by biallelic variants in CCN6. This study aimed to describe the early signs and follow-up findings in 44 Turkish PPRD patients.The patients with progressive stiffness of multiple joints, characteristic wide metaphysis of interphalangeal (IP) joints and platyspondyly were clinically diagnosed with PPRD. Fifteen patients who had first symptoms under 3 years of age were grouped as early-onset, while others were grouped as classical. CCN6 sequencing was performed in 43 patients.Thirteen pathogenic/likely pathogenic variants were identified, five were novel. c.156C>A(p.Cys52*) variant was found in 53.3% of the families. The initial symptom in the early-onset group was genu varum deformity, while it was widening of IP joints in the classical group. The median age of onset of symptoms and of diagnosis was 4 and 9.7 years, respectively. The mean follow-up duration was 5.6 years. The median age of onset of IP, elbow, knee and hip stiffness, which became progressive with growth was 5, 9, 9 and 12.2 years, respectively. Waddling gait occurred in 97.7% of the patients. A total of 47.7% lost independent walking ability at the median age of 12 years. In the early-onset group, waddling gait occurred earlier than in classical group (P < 0.001). Two patients had atypical presentation with late-onset and mild or lack of IP involvement.We observed that genu varum deformity before the age of 3 years was an early sign for PPRD and almost half of the patients lost walking ability at the median age of 12 years.