INPP5E and Joubert syndrome: INPP5E (MIM: 613037) mutations cause JBTS1 and were identified in a cohort of JBTS-affected individuals with mainly neurological features and some retinopathy but without kidney disease or polydactyly,34 suggesting a lack of Hedgehog signaling defects.35, 36 In contrast, NPHP3 (MIM: 608002) mutations were initially identified as causing an adolescent form of nephronophthisis, a progressive form of renal failure.37