PRG4 and camptodactyly-arthropathy-coxa vara-pericarditis syndrome: Pathogenic variants in PRG4 identified on chromosome 1q25-q31 cause the CACP syndrome, characterized by congenital or early-onset camptodactyly, childhood-onset non-inflammatory arthropathy of large joints - such as elbows, hips, knees, and ankles - synovial hyperplasia, progressive coxa vara deformity and non-inflammatory pericardial or pleural effusion (Albuhairan and Al-Mayouf, 2013; Vutukuru and Reddy, 2016).