Cystinuria is an inherited disease that causes a specific type of kidney stones.
What is going on in the body?
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.
What are the causes and risks of the disease?
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.
What can be done to prevent the disease?
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.
How is the disease diagnosed?
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.
Long Term Effects
What are the long-term effects of the disease?
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.
What are the risks to others?
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.
What are the treatments for the disease?
The goals of treatment for cystinuria are primarily pain relief and prevention of kidney stones.
Recommendations may include:
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
What are the side effects of the treatments?
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.
What happens after treatment for the disease?
Even after kidney stones have been successfully treated, new stones may form.
How is the disease monitored?
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.
Scriver CR et al: The Metabolic and Molecular Basis of Inherited Disease. McGraw Hill, 1995
Buyse ML: Birth Defects Encyclopedia. Blackwell Scientific Publications, 1990