Noteworthy, PKD is a recognized phenotypic trait of HANAC (hereditary angiopathy, nephropathy, aneurysms, and muscle cramps) syndrome, an autosomal dominant disorder determined by heterozygous pathogenetic variants in the COL4A1 (Collagen, Type IV, α-1; MIM: 120130) gene [36]. Here, COL4A1 is linked to Down syndrome.