MUC1 and familial juvenile hyperuricemic nephropathy: Finally, we evaluate Ca2+ levels in patients with MUC1 mutation causing autosomal dominant, tubulointerstitial kidney disease (ADTKD-MUC1) to determine whether MUC1 mutation results in haploinsufficiency, causing reduced blood Ca2+ levels as compared to control patients with autosomal dominant, tubulointerstitial kidney disease due to mutation in UMOD, encoding uromodulin (ADTKD-UMOD).