To further investigate our hypothesis that the VNTR might be a mutational hotspot prone to other mutations (e.g. small deletions etc.)within or outside of the 7C homopolymer a small cohort of three large families (F12, F13, and F16), three smaller families (F10, F14 and F15) and one sporadic case (F11), all compatible with a diagnosis of ADTKD-MUC1, were analysed (Table 2, Fig. 4b). This evidence concerns the gene MUC1 and autosomal dominant medullary cystic kidney disease with or without hyperuricemia.