Long-term follow-up of patients with idiopathic infantile hypercalcaemia.

Idiopathic infantile hypercalcaemia (IIH) is a rare disorder of unknown etiology that presents with hypercalcaemia in a child's first year of life. There is only a limited number of published reports of the natural history of this condition, and the long-term prognosis is largely unknown. The presentation, treatment and long-term follow-up of 11 children with IIH treated at our institution since 1993 are described. Hypercalcaemia resolved in the majority of children by the time they were 3 years of age, but nephrocalcinosis and persistent hypercalciuria were common, and, in some cases, urinary calcium excretion increased after initially becoming normal. This study suggests that clinical and biochemical abnormalities may persist for longer than previously reported and implies the need for ongoing surveillance of patients with IIH.