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Diseases

Genetic and Rare Diseases Information Center (GARD)

Alkaptonuria


Other Names for this Disease
  • AKU
  • Alcaptonuria
  • Ochronosis, hereditary
  • Alkaptonuric ochronosis
  • Homogentisic acid oxidase deficiency
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.

Your Question

My husband, now 44 years of age, was diagnosed with alkaptonuria 10 years ago. Until recently, he experienced discoloration of the urine, occasional stiff joints, and rupture of tendons. Now he is having breathing problems and stomach issues. Are these symptoms related to alkaptonuria? Are there any treatments for this condition? Are there dietary guidelines for individuals with alkaptonuria?

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What are the signs and symptoms of alkaptonuria?

The three main features of alkaptonuria (AKU) are the presence of  a substance called homogentisic acid (HGA) in the urine, ochronosis and arthritis. The urine of individuals with AKU turns black when exposed to air. Children do not have symptoms of AKU other than the urine turning black when left to stand for a few minutes. Ochronosis, a buildup of dark pigment in connective tissues such as cartilage and skin, is also characteristic of the disorder. This blue-black pigmentation usually appears after age 30 and commonly affects the cartilage of the ear, ligaments, tendons, blood vessels, kidneys, lungs and prostate. Dark spots on the white of the eye and cornea may also occur. People with alkaptonuria typically develop arthritis, particularly in the spine and large joints, beginning in early adulthood. Other features of this condition can include heart problems, kidney stones, changes of the sound of the voice and prostate stones.[1][2][3]
Last updated: 3/18/2016

Are breathing problems and stomach issues commonly reported in individuals with alkaptonuria?

Breathing problems and stomach issues are not classic symptoms of alkaptonuria, although cardiovascular problems may present in later adulthood and the pigmentations associated with the condition may affect the lungs (as well as many other body systems).[1][3]
Last updated: 3/18/2016

How might alkaptonuria be treated?

There is no cure for alkaptonuria, but there is treatment for some individual signs and symptoms of the condition. Joint pain may be substantial in individuals with alkaptonuria, and close attention to pain control is usually necessary. Physical and occupational therapy can be important to promote muscle strength and flexibility. Knee, hip, and shoulder replacement surgeries may be options for managing significant arthritis. In general, however, the goal of joint replacement is pain relief rather than increased range of motion. Maintaining joint range of motion through moderate non-weight-bearing exercise such as swimming may have beneficial effects. Treatment of prostate stones and renal stones may include surgery.[4]

Several therapies for alkaptonuria have been investigated. Treatment of alkaptonuria with nitisinone (also called NTBC) has been proposed; nitisinone is currently approved for the treatment of tyrosinemia type I, which is also a metabolic disorder. Further investigations to determine the benefits of nitisinone in slowing the progression of joint disease are in progress.Oral bisphosphonate therapy has been suggested to halt the progressive bone loss but studies have not confirmed the benefit.[4] To see a list of completed clinical trials or trials currently enrolling individuals with alkaptonuria, click here.

No therapy has proven to prevent or correct the pigmentary changes of ochronosis.

Dietary restriction of phenylalanine and tyrosine has been proposed to reduce the production of HGA, but severe restriction of these amino acids is not practical in the long term and may be dangerous.[4]
Last updated: 3/18/2016

Are there any dietary guidelines for individuals with alkaptonuria?

Information supporting dietary management of alkaptonuria is limited. Dietary restriction of phenylalanine and tyrosine has been showed to reduce the production of homogentistic acid, in children, but severe restriction of these amino acids is not practical in the long term and may be dangerous. In an adult, a similar restriction reportedly had no effect on excretion of the abnormal metabolite. Whether a mild dietary restriction from early in life would avoid or minimize later complications is not known. Nonetheless, high-protein diets should be avoided. High doses of vitamin C, as much as 1 g/d, is recommended for older children and adults, and may decrease urinary benzoquinone acetic acid, a derivative of homogentistic acid, but do not appear to affect homogentistic acid excretion. It has been hypothesized that high-dose ascorbic acid may prevent the deposition of ochronotic pigment, although it does not alter the basic metabolic defect.[4][5]
Last updated: 8/1/2011

References
Other Names for this Disease
  • AKU
  • Alcaptonuria
  • Ochronosis, hereditary
  • Alkaptonuric ochronosis
  • Homogentisic acid oxidase deficiency
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.