The inositol polyphosphate 5-phosphatase (INPP5E) mutations cause Joubert syndrome 1 (MIM:213300), a clinically and genetically heterogeneous group of disorders that are characterized by midbrain-hindbrain malformation and various associated ciliopathies that include retinal dystrophy, nephronophthisis, liver fibrosis, and polydactyly. Here, INPP5E is linked to nephronophthisis.