Dear Editor

The recent report on Malignant Infantile Osteopetrosis (MIOP) presenting with neonatal hypocalcaemia highlights the importance of early recognition of a rare but treatable disorder.[1]

We would like to point out that recognition in the neonate is difficult, as many of the characteristic manifestations have not had time to develop. The normal sequence of events leading to the diagnosis being made is usually via a known family history or by radiologists commenting on increased bone density, seen on x-ray.

In our experience of two related siblings, the mode of presentation, in prematurity, was through a fracture of a long bone. This has not been reported previously in the preterm neonate.

A suggested hypothesis is that the imbalance of osteoblast and osteoclast function, which is represented in the article as leading to hypocalcaemia, also leads to faulty and haphazard bone modelling, thus making osteopetrotic bones prone to fractures.

ANIRBAN MAJUMDAR
Alder Hey Children’s Hospital
Liverpool, UK

NICK WILD
Warrington District General Hospital
Warrington, UK

Reference

(1) Srinivasan M, et al. Malignant infantile osteopetrosis presenting with neonatal hypocalcaemia. Arch Dis Child Fetal Neonatal Ed 2000;83:F21-3.