Cystinuria

Cystinuria

Autosomal recessive hereditary defect in Amino acid transporter in Renal Proximal convoluted tubules and intestine.

There is impaired resorption of Cysteine, Ornithine, Lysine, Arginine (COLA), in PCT and intestine.

If these amino acids are not reabsorbed, they are excreted in urine in excess.

Excessive cysteine in urine can lead to recurrent precipitation of hexagonal cystine stones.

Two cysteines attached with disulphide bond makes Cystine.

Urinary cyanide Nitroprusside test is diagnostic and shows magenta-red color.

Treatment:

Hydration – increased water intake dissolve small stones and reduces further precipitation.

Alkalinization- keeping Urine alkalinized reduces chances of cystine precipitation and stone formation. It also helps in dissolving stones.

Chelation- penicillamine or Tiopronin chelates cystine and reduces urinary excretion and stone formation.

Case Scenario

12-year-old girl presented to pediatrician with chief complaints of sudden sever right flank pain associated with nausea and vomiting. On physical examination tenderness in the right upper quadrant and flank is noticed. Urine examination shows pus cells, increased leukocytes and hexagonal crystals. Urine sodium nitroprusside test shows magenta-red color.

Which is the most likely diagnosis and treatment?