Disorders of the renal proximal tubule.

Following glomerular filtration, the bulk of solutes are reabsorbed in the proximal tubule to prevent excessive losses of vital metabolites. In this nephron segment, reabsorption is largely active via dedicated transporters. Hereditary defects in proximal tubular function are characterized by malabsorption affecting amino acids, glucose, potassium, phosphate, bicarbonate, low-molecular-weight proteins and other solutes handled by this nephron segment. Dysfunction may be isolated or generalized (Fanconi syndrome). Defects in specific transporters lead to increased urinary excretion of substrates, which are often diagnostic. In others, extrarenal gene expression causes a multisystem phenotype. In this review, we will give a short overview of the molecular genetics, clinical picture, pathophysiology and treatment of genetically defined proximal tubulopathies.