Fig. (2) Hereditary Disorders of the Proximal Tubule. Hereditary renal glucosuria is caused a mutated sodium-glucose transporter SLGT2. A mutated bAT1 or rBAT protein, which make up the luminal cystine and dibasic aminoacid transporter leads to cystinuria. Proximal RTA can be caused by a mutated carbonic anhydrase II (CA2) or the basolateral membrane sodium-bicarbonate transporter (NBC1). Hereditary hypophosphatemic rickets is caused by a mutated sodium-phosphate transporter in the luminal membrane. Hereditary hypouricemia is caused by a mutated urate transporter URAT1. A mutated cystinosin in the lysosomal membrane leads to cystine storage and Fanconi syndrome (FS). Mutated phosphotylinositol-4,5-biphosphate 5-phosphatase (INPP5P) in the Golgi apparatus leads to Lowe syndrome and FS. FS is also caused by a mutation in the CLC-5 chloride channel in the endosome leading to impaired recycling of megalin.