Cistinuria: la importancia del sedimento

Cystinuria is caused by the excess of an amino acid called cystine (amino acid dimer cysteine), in the urine. It was first described at the beginning of the 19th century. It is a congenital metabolic disease with an autosomal recessive inheritance pattern. It is characterised by a defect in transport, which affects certain dibasic amino acids, cystine, ornithine, lysine, and arginine in its reabsorption into the renal tubule and gastrointestinal tract. As a result, only cystine (due to its great insolubility in acid urine owing to increased excretion and supersaturation in urine), promotes the formation of crystals or precipitates that form stones. The case is presented of an adult with cystinuria, who was diagnosed by the crystals found in the urinary sediment, after making a differential diagnosis with the crystals of anhydrous cholesterol, with which they can be confused.