PAX2 and cyst: As our study has shown, small- to normal-sized kidneys with or without cyst formation or changes in corticomedullary differentiation can be caused by mutant NPHP and HNF1B genes (Chaki et al., 2011; Avni et al., 2015), whereas mutations in PAX2 lead to small-sized kidneys that often show distinct corticomedullary differentiation and no cysts (Bower et al., 2012).