Congenital Lactase Deficiency, An Unusual Cause of Infantile Hypercalcemia.

Infantile hypercalcemia is an uncommon presentation, even for a pediatric endocrinologist. However, the combination of diarrhea and hypercalcemia makes the situation particularly intriguing. In this report, the authors present the case of an infant referred to them for hypercalcemia, who had been experiencing watery diarrhea, abdominal distension, and failure to thrive since early neonatal age. The eventual diagnosis was congenital lactase deficiency. Targeted management with lactose-free feeds normalized calcium levels within a week of starting the therapy. During the first follow-up visit, three weeks after discharge, she exhibited a normal metabolic profile with optimum catch-up growth.