Transient neonatal hyperparathyroidism: a presenting feature of sialidosis type II.

Sialidosis is a lysosomal storage disease caused by deficiency of α-N-acetyl neuraminidase-1. Sialidosis is classified into two main clinical variants: type I, the milder form of the disease, and type II, which can in turn be subdivided into three forms: congenital, infantile, and juvenile. We report a female patient with sialidosis type II, presenting with the congenital form of the disease with thrombocytopenia, pulmonary interstitial thickening, and transient secondary neonatal hyperparathyroidism.