Cystinuria

Cystine is one of the essential amino acids, which are the building blocks of protein. In people with cystinuria, a large amount of cystine is concentrated in the urine. The concentrated cystine leads to the formation of kidney stones.

The symptoms of cystinuria include:

• pain in the side, back, or groin
• blood in the urine
• frequent urination
• pain or burning during urination
• the formation of kidney stones

Cystinuria is an autosomal recessive disease, which means that a person with the disease has inherited two copies of a defective gene. Cystinuria affects 1 in 10,000 people worldwide.

Nothing can be done to prevent cystinuria. Drinking large amounts of water helps reduce kidney stone formation. The water also helps stones pass through the urinary tract.

Cystinuria should be suspected in people younger than 30 years who have kidney stones. The kidney stones caused by cystinuria are yellow-brown in color and 6-sided. Diagnosis is confirmed by finding large amounts of cystine in the urine.

Frequent urinary tract infections may occur in someone with cystinuria. Obstruction of the urinary tract may result. A person cystinuria may rarely develop kidney failure, which can shorten the person's lifespan.

Parents who have had a child with cystinuria are at risk to have other children with this condition. One in 4 pregnancies for parents carrying this genetic disorder is expected to result in a child born with cystinuria. Since the gene is recessive, both parents must carry and pass on the defective gene in order for the child to have cystinuria. Genetic counseling may be useful for couples with a family history of the disease.

The goals of treatment for cystinuria are primarily pain relief and prevention of kidney stones.

Recommendations may include:

• pain medications
• drinking large amounts of water to dilute the cystine and reduce stone formation
• sodium bicarbonate or medications such as acetazolamide (i.e., Diamox) to reduce stone formation
• medications to bind cystine and reduce the amount available for stone formation
• ultrasound treatments (i.e., lithotripsy) to break stones apart and help them pass along the urinary tract
• surgery to remove larger stones
• dialysis or kidney transplant if the person develops kidney failure

Side effects vary, depending on the treatments used. All medications have side effects, including allergic reactions to the medication. Surgery carries a risk of bleeding, infection, or a reaction to the anesthesia.

Even after kidney stones have been successfully treated, new stones may form.

Periodic kidney function tests will be done to detect early signs of kidney failure in a person with cystinuria. Any new or worsening symptoms should be reported to the healthcare professional.