Multicentric carpo-tarsal osteolysis: the importance of imaging studies, genetic findings and clinical expertise in differential diagnosis and follow-up-a case report.

Multicentric carpotarsal osteolysis (MCTO) is a very rare skeletal disorder marked by progressive bone resorption, predominantly affecting carpal and tarsal bones. It results from a MAFB gene mutation, leading to increased osteoclastic activity and bone loss. The condition may also involve renal impairment and subtle craniofacial anomalies. Due to overlapping features, MCTO is often misdiagnosed as juvenile idiopathic arthritis (JIA). We report the case of a 10-year-old patient, who initially avoided using the hands while crawling. By age three, the patient developed a limping gait and joint pain. Imaging showed carpal and tarsal bone resorption suggestive of MCTO, later confirmed by a disease-causing MAFB variant. Treatment with methotrexate, naproxen, and intra-articular triamcinolone improved symptoms and resolved inflammation-related anemia and thrombocytosis, but radiographic progression persisted despite clinical improvement. This case highlights the challenge of distinguishing MCTO from JIA and underscores the importance of integrating clinical, lab, and imaging data for accurate diagnosis. Immunosuppressive therapy may be associated with symptomatic relief, although not halting disease progression. Further research is needed to identify more effective treatment.