Cystinuria

Cystinuria (OMIM #220100) is an autosomal recessive disorder of a dibasic amino acid transport in the apical membrane of epithelial cells of the renal proximal tubule and small intestine. It leads to increased urinary cystine excretion and recurrent urolithiasis. The cystine transporter is an heterodimeric transporter which is composed of a heavy subunit, rBAT, linked to a light subunit, b0,+AT. Two genes, SLC3A1 (solute carrier family 3 member 1) and SLC7A9, coding for rBAT and b0,+AT, account for the genetic basis of cystinuria. Cystinuria may lead to obstruction, infections, and ultimately to renal insufficiency. The diagnosis of cystinuria mainly relies on stone analysis, urinary cystine measurement, or urinary cystine crystal identification. Medical treatment is based upon a stepwise strategy using hydration and alkalinization as basic measures, with the addition of thiol derivatives in refractory cases. Urological interventions are often indicated for the management of cystine stones >5 mm in diameter.