MUC1 and autosomal dominant medullary cystic kidney disease with or without hyperuricemia: The prototypic causative variant in MUC1 associated ADTKD, the insertion of a eighth cytosine base (insC) in a seven cytosine stretch within one unit of the VNTR composed of almost identical 60-mer units (according to HGVS nomenclature recommendations a duplication, but for the sake of clarity we stay with term insertion used in most publications), has been repeatedly found worldwide (also arbitrarily referred to as c.428dupC)4,5.