Phenotype of Idiopathic Infantile Hypercalcemia Associated with the Heterozygous Pathogenic Variant of and .

Idiopathic infantile hypercalcemia (IIH) is a rare genetic disease, also called hypersensitivity to vitamin D3. The molecular heterogeneity allows for the differentiation between the two forms; IIH type 1 caused by genetic variants and IIH type 2 associated with mutations. The affected individuals express a variety of symptoms: hypercalcemia, hypercalciuria, suppressed intact parathormone levels (PTH), nephrocalcinosis, elevated levels of serum 1,25 (OH)2-vitamin D3 or inappropriately normal levels, and kidney phosphate wasting. The present paper describes three cases of IIH with heterozygous mutations in and genes, respectively. The genetic diagnosis is of paramount importance for proper treatment and the prediction of long-term outcomes.