Disease or Syndrome
alkaptonuria
[ al-kap-tuh-noo r-ee-uh, -nyoo r- ]
Subclass of:
Amino Acid Metabolism, Inborn Errors
Etymology:
Arabic al = the + kali or qalig = soda ash + Greek haptein = to seize + ouron = urine
Definitions related to alkaptonuria:
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A rare autosomal recessive disorder characterized by abnormalities in the metabolism of phenylalanine and tyrosine. It results in the accumulation in the blood of homogentisic acid which is excreted in the urine. The presence of homogentisic acid in the urine causes its color to turn black. The excessive amount of homogentisic acid in the blood may cause damage to cartilage and heart valves, and may result in the formation of kidney stones.NCI ThesaurusU.S. National Cancer Institute, 2021
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Alkaptonuria is caused by deficiency of homogentisate 1,2-dioxygenase, an enzyme that converts homogentisic acid (HGA) to maleylacetoacetic acid in the tyrosine degradation pathway. The three major features of alkaptonuria are dark urine or urine that turns dark on standing, ochronosis (bluish-black pigmentation in connective tissue), and arthritis of the spine and larger joints. Ochronosis generally occurs after age 30 years; arthritis often begins in the third decade. Other manifestations can include pigment in the sclera, ear cartilage, and skin of the hands; aortic or mitral valve calcification or regurgitation and occasionally aortic dilatation; renal stones; prostate stones; and hypothyroidism.GeneReviewsUniversity of Washington, 2021
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An inborn error of amino acid metabolism resulting from a defect in the enzyme HOMOGENTISATE 1,2-DIOXYGENASE, an enzyme involved in the breakdown of PHENYLALANINE and TYROSINE. It is characterized by accumulation of HOMOGENTISIC ACID in the urine, OCHRONOSIS in various tissues, and ARTHRITIS.NLM Medical Subject HeadingsU.S. National Library of Medicine, 2021
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Alkaptonuria is one of 4 disorders originally defined as an inborn error of metabolism by Archibald Garrod in his Croonian Lectures of 1902. The hallmark of the disease is passage of urine that becomes black when left standing.WebMD, 2019
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Alkaptonuria is an inherited condition that causes urine to turn black when exposed to air. The three major features of alkaptonuria are the presence of dark urine, ochronosis, a buildup of dark pigment in connective tissues such as cartilage and skin, and arthritis of the spine and larger joints. Ochronosis starts after age 30 and...National Center for Advancing Translational Sciences
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Alkaptonuria, rare (one in 250,000 to 1,000,000 births) inherited disorder of protein metabolism, the primary distinguishing symptom of which is urine that turns black following exposure to air. It is characterized biochemically by an inability of the body to metabolize the amino acids tyrosine and...Encyclopedia Britannica, Inc., 2020
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