Syndrome of progressive deforming non-inflammatory arthritis of childhood: two patients of camptodactyly-arthropathy-coxa vara-pericarditis syndrome

Camptodactyly-arthropathy-coxa vara-pericarditis (CACP) syndrome is a rare familial arthropathy of childhood, commonly misdiagnosed as juvenile idiopathic arthritis. It is characterized by non-inflammatory arthropathy, coxa vara deformity, and sterile pericarditis. We describe two children with CACP syndrome who were referred to the rheumatology clinic for the suspicion of inflammatory arthritis. A literature search was carried out using PubMed/ Medline and Embase databases. English language reports of mutation-proven cases of CACP syndrome reported until 31 March 2020 were retrieved and analysed. Both the children had a delay in diagnosis (age at diagnosis- 12 and 13 years, respectively) and had received immunomodulatory therapy for suspected inflammatory arthritis. Presence of symmetrical arthropathy of large joints, camptodactyly, and normal inflammatory parameters are clues that indicated CACP syndrome. One child with a novel variant in PRG4 also had associated mitral valve prolapse and regurgitation. Both had severe constrictive pericarditis requiring pericardiectomy. On literature review, a total of 98 mutation-proven cases of CACP syndrome have been reported till date. Arthropathy in CACP syndrome mainly involves knees, wrists, ankles, and hips. Pericarditis is usually mild, however, can present rarely with severe symptoms requiring surgical intervention. CACP syndrome can closely mimic inflammatory arthritis and early clinical recognition is important to avoid misdiagnosis. Molecular confirmation is essential for early diagnosis and future genetic counselling for affected families.