Autosomal dominant hypocalcemia type 1 (ADH1) patients are heterozygous for a gain-of-function mutant CASR. Treatment of ADH1 patients with active vitamin D upregulates the oversensitive renal CaSR stimulating Ca2+ excretion provoking nephrocalcinosis, nephrolithiasis, and potential renal damage (Pearce et al., 1996; Lienhardt et al., 2001). Here, CASR is linked to autosomal dominant hypocalcemia 1.