What is cystinuria
and what are its symptoms?
Cystinuria is a genetic disease characterized by a buildup of the amino acid cystine in the kidneys and bladder.
These high levels of cystine lead to the formation of cystine stones in the kidneys, ureter and bladder. These cystine stones generate various complications, such as hypertension, intense abdominal pain, recurrent urinary tract infections, renal function impairment in up to 70% of patients and chronic renal insufficiency. These complications can ultimately lead to renal failure.
Signs and symptoms of the condition are related to the presence of stones and may include nausea, hematuria (blood in the urine), flank pain and/or frequent urinary tract infections.
There are estimated to be 40,000 and 25,000-35,000 patients with cystinuria in Europe and the United States, respectively.
How is cystinuria treated?
In order to prevent cystine stones, cystinuric patients require around-the-clock control of their urine pH. Treatment of cystinuria involves the combination of 1) alkalizing treatments to increase urine pH for higher cystine solubility, 2) hyperdiuresis, which reduces cystine concentration by increasing urine production and excretion, and 3) a protein-poor diet, since proteins are high in cystine.
Of the available alkalizing therapies for the management of cystinuria, citrate is the intervention of choice as citrate excretion in urine potentially prevents calcium salt crystallization in alkali conditions (over a pH of 7.5). Potassium salts do not lead to the adverse consequences observed with sodium salts, which had been historically used as an alkalizing therapy. Moreover, it is recommended that potassium deficiency be avoided in cystinuria patients since this condition may decrease citrate excretion and cause renal acidosis; a buildup of acids in the blood.
There are currently no approved drugs specifically indicated for the treatment of Cystinuria, including potassium citrate/potassium bicarbonate.