PKD1 and autosomal dominant polycystic kidney disease: Similarly, patients with higher MCIC risk classes (1A-1B, to 1C, and 1D-1E) were also enriched with mutation classes (i.e. PKD1 truncating mutations, PKD1 inframe indels, and complex bilineal or digenic mutations) that are typically associated with more rapid rate of ADPKD progression (Fig. 2)4,5,12.