Patients with the autosomal recessive disorder camptodactyly-arthropathy-coxa vara-pericarditis syndrome (CACP) caused by mutations in PRG4 have joints that appear normal at birth, but over time develop severe degeneration of the cartilage surface and synoviocyte hyperplasia leading to precocious joint failure [11]. The gene discussed is PRG4; the disease is camptodactyly-arthropathy-coxa vara-pericarditis syndrome.