Osteopetrorickets and calcium homeostasis in children with osteopetrosis: an endocrinological single-center study

Abstract

Background Osteopetrosis is a rare inherited disorder caused by impaired osteoclast number or function, leading to increased bone density, fractures, neurologic complications, and disturbances in calcium-phosphate homeostasis. This study aimed to describe the endocrine manifestations of childhood osteopetrosis, particularly osteopetrorickets, and to evaluate treatment responses and post-transplant calcium disorders. Methods We retrospectively reviewed 17 children diagnosed with osteopetrosis at a single tertiary center between 2015 and 2025. Clinical, biochemical, radiologic, genetic, and treatment data were analyzed. Results The median age at diagnosis was 14 months (range, 15 days–130 months), and short stature was observed in 13 of 17 patients (76.4%). Ophthalmologic abnormalities were present in 10 patients (58.8%), hearing loss in 7 patients (41.1%), and hepatosplenomegaly in 7 patients (41.1%). TCIRG1 was the most frequent mutation, followed by CLCN7, TNFSF11, TNFRSF11A, and CA2. Osteopetrorickets was identified in 13 of 17 patients (76.4%); among these patients, hypocalcemia occurred in 11 of 13, hypophosphatemia in 8 of 13, and vitamin D deficiency in 4 of 13. Generalized osteosclerosis was observed in all patients, whereas classic osteopetrosis-associated radiographic findings, including bone-in-bone appearance, sandwich vertebrae, and Erlenmeyer flask deformity, were identified only in a subset of patients. Hematopoietic stem cell transplantation was performed in 11 of 13 patients with osteopetrorickets. Four of these 11 patients died during the early post-transplant period. Among patients with osteopetrorickets who underwent hematopoietic stem cell transplantation (HSCT) (n=11), seven surviving patients achieved complete resolution of rickets (7/11, 63.6%), allowing discontinuation of replacement therapy within 15 days to 8 months. Post-transplant hypercalcemia developed in 4 of 13 transplant recipients (30.8%). Conclusions Osteopetrorickets is a frequent and clinically significant complication of pediatric osteopetrosis. Early recognition of mineral disturbances, genotype-based treatment planning, and close surveillance for rebound hypercalcemia after transplantation are essential to improve outcomes.