Malignant infantile osteopetrosis presenting with neonatal hypocalcaemia

Presentation characteristics were reviewed in 14 children from 12 families with malignant infantile osteopetrosis seen at two large referral centres f or bone marrow transplantation. Children from six of these families present ed initially with symptoms of hypocalcaemia. These comprised early or late neonatal convulsions in six cases (corrected serum calcium < 1.5 mmol/l), a nd vomiting and irritability (serum calcium 1.68 mmol/l) in another. One ot her related child had severe and persistent littering episodes almost certa inly attributable to hypocalcaemia. In seven of eight cases, these symptoms developed during the first 14 days of life. Although occasionally reported previously, malignant infantile osteopetrosis remains essentially unrecogn ised as a cause of neonatal hypocalcaemia, often resulting in diagnostic co nfusion and delay. This is important in the context of curative haemopoieti c stem cell transplantation where preservation of sight may depend on early intervention.