Alkaptonuria (patient information)
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What is Alkaptonuria?
Alkaptonuria is a rare condition in which a person's urine turns a dark brownish-black color when exposed to air.
What are the symptoms of Alkaptonuria?
Urine in an infant's diaper may darken and can turn almost black after several hours. However, many persons with this condition may not know they have it until mid-adulthood (around age 40), when joint and other problems occur.
Symptoms may include:
- Arthritis (especially of the spine) that gets worse over time
- Darkening of the ear
- Dark spots on the white of the eye (sclera) and cornea
How to know you have Alkaptonuria?
A urine test (urinalysis) is done to test for alkaptonuria. If ferric chloride is added to the urine, it will turn the urine a black color in patients with this condition.
When to seek urgent medical care
Call your health care provider if you notice that your own urine or your child's urine becomes dark brown or black when it is exposed to air.
Treatment options
Some patients benefit from high-dose vitamin C. This has been shown to decrease the build-up of brown pigment in the cartilage and may slow the development of arthritis.
Diseases with similar symptoms
- Ankylosing Spondylitis[1]
- Acute intermittent porphyria[1]
Where to find medical care for Alkaptonuria
Directions to Hospitals Treating Alkaptonuria
Prevention of Alkaptonuria
There is no know prevention of alkaptonuria.
What to expect (Outlook/Prognosis)
The outcome for people affected with alkaptonuria is generally expected to be good. Some possible complications include people with this condition also can get arthritis in adulthood. The build-up of homogentisic acid in the cartilage causes arthritis in about 50% of older adults with alkaptonuria.
- Homogentisic acid also can build up on the heart valves, especially the mitral valve. This can sometimes lead to the need for valve replacement.
- Coronary artery disease may develop earlier in people with alkaptonuria.
- Kidney stones and prostate stones may be more common in people with alkaptonuria.