Neonatal hypocalcemia and hydrocephalus as early manifestations of intermediate osteopetrosis: successful hematopoietic stem cell transplantation despite negative genetic testing: a case report.

Osteopetrosis is a rare genetic skeletal disorder caused by defective osteoclast-mediated bone resorption, leading to increased bone density and complications including hypocalcemia, pancytopenia, cranial nerve compression, and, more rarely, hydrocephalus. We report a rare case of intermediate osteopetrosis presenting with neonatal hypocalcemia and progressive macrocephaly. Brain magnetic resonance imaging confirmed obstructive hydrocephalus, which was treated with ventriculoperitoneal shunting. Clinical and radiological findings supported the diagnosis of osteopetrosis, although targeted genetic testing and whole exome sequencing did not identify a causative variant. The patient was treated with calcium gluconate and vitamin D supplementation, followed by hematopoietic stem cell transplantation from an HLA-matched unrelated donor using peripheral blood stem cells. This case highlights the importance of early recognition and timely hematopoietic stem cell transplantation to promote successful engraftment and improve long-term outcomes, even in the absence of molecular confirmation.