Genetic findings that modified the diagnosis in 19 patients included mutations in patients with NPHP (NPHP1 [n = 4], TTC21B [n = 3], ANKS6 [n = 1], NPHP3 [n = 1], NPHP4 [n = 1]), collagenopathies (COL4A5 [n = 7], COL4A3 [n = 1]), and Fabry disease (GLA [n = 1]). The gene discussed is TTC21B; the disease is Fabry disease.