Camptodactyly–Arthropathy–Coxa Vara–Pericarditis Syndrome without Camptodactyly: A Pediatric Case and Review of the Literature

BACKGROUND: Camptodactyly-arthropathy-coxa vara-pericarditis syndrome is a rare autosomal recessive disorder with camptodactyly, non-inflammatory arthropathy, coxa vara, and pericarditis. Symptoms usually begin in early childhood with swelling of interphalangeal joints, wrists, and knees. Pericarditis is rare. It is caused by proteoglycan 4 gene mutations and often misdiagnosed as juvenile idiopathic arthritis due to overlapping features. CASE PRESENTATION: A 4-year-old boy presented with 6 months of knee and wrist swelling and nocturnal pain. His parents were first-degree cousins, and a maternal uncle had rheumatoid arthritis. He had prior hip surgeries at 2.5 years. Examination showed swelling in knees, ankles, and wrists, and 30° wrist extension limitation. No systemic symptoms were noted. The erythrocyte sedimentation rate, C-reactive protein level, and antinuclear antibody test results were normal. Magnetic resonance imaging showed effusion and synovial thickening. Initially diagnosed with polyarticular juvenile idiopathic arthritis, he received methotrexate and etanercept. Due to progressive gait issues and radiographic coxa vara, diagnosis was revised. Genetic testing confirmed homozygous proteoglycan 4 (c.915delC) mutation. CONCLUSIONS: This case underscores an atypical camptodactyly-arthropathy-coxa vara-pericarditis presentation without camptodactyly. Persistent non-inflammatory arthropathy despite immunosuppression should raise suspicion for camptodactyly-arthropathy-coxa vara-pericarditis.