Transient neonatal hyperparathyroidism: a presenting feature of mucolipidosis type II

The phenotype of mucolipidosis type II (ML II), a disorder of lysosomal enzyme transport, includes mucopolysaccharidosis type I (Hurler syndrome)-like features and dysostosis multiplex, usually apparent after 6 months of age. We describe here the natural history of neonatal hyperparathyroidism, a recently described presentation of ML II. A female neonate presented with multiple fractures and radiological features of osteopenia and 'rickets-like' changes. Longitudinal evaluation, while the patient was treated with vitamin D 800-3,000 IU/day orally, indicated secondary hyperparathyroidism which resolved, biochemically and radiologically, by age 4 months. Neonatal hyperparathyroidism in ML II is severe, transient, and probably secondary to impaired placental calcium transport, simulating a condition observed in the offspring of chronically hypocalcemic mothers.