Lenherr-Taube N, Furman M, Assor E, et al. - Researchers conducted this longitudinal, observational cohort study to describe the clinical and biochemical response to dietary calcium and vitamin D restriction in a genetically characterized cohort of mild idiopathic infantile hypercalcemia (IIH). The sample consisted of 20 children with mild IIH monitored for a median of 21 months. Individuals with CYP24A1 or SLC34A1/A3 variants showed no differences in response. Mild IIH has a variable clinical presentation, and dietary calcium and vitamin D restriction does not consistently normalize elevated 1,25(OH)2D concentrations or prevent renal calcification worsening in all cases. Therapeutic options should target the vitamin D metabolism defect.