Alkaptonuria
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What is alkaptonuria?
Alkaptonuria is an inherited condition that causes urine to turn black when exposed to air. Ochronosis, a buildup of dark pigment in connective tissues such as cartilage and skin, is also characteristic of the disorder. People with alkaptonuria typically develop arthritis in adulthood, particularly in the spine and large joints.
How common is alkaptonuria?
The condition is rare, affecting 1 in 250,000 to 1 million people worldwide. Alkaptonuria is more common in certain areas of Slovakia (where it has an incidence of about 1 in 19,000 people) and in the Dominican Republic.
What genes are related to alkaptonuria?
Mutations in the HGD gene cause alkaptonuria.
The HGD gene makes an enzyme called homogentisate oxidase, which helps break down the amino acids phenylalanine and tyrosine (important building blocks of proteins) into smaller molecules. Mutations in the HGD gene prevent the enzyme from playing its role in this process. As a result, a substance called homogentisic acid builds up in the body. Excess homogentisic acid is deposited in connective tissues, which causes cartilage and skin to darken and leads to arthritis. Homogentisic acid is also in present in urine, which makes the urine turn dark when exposed to air.
How do people inherit alkaptonuria?
This condition is inherited in an autosomal recessive pattern, which means two copies of the gene in each cell are altered. Most often, the parents of an individual with an autosomal recessive disorder each carry one copy of the altered gene but do not show signs and symptoms of the disorder.
Source: National Institutes of Health
Research from Hebei Medical University in arthritis provides new insights
2009 AUG 10 - (NewsRx.com) -- According to recent research from Shijiazhuang, People's Republic of China, "Alkaptonuria is a rare disease in which the body does not have enough of an enzyme called homogentisic acid oxidase. Osteoarthritis is the most common degenerative joint disease." "Ochronotic arthritis which resulting from the deposition of oxidized homogentisic acid within the connective tissues of peripheral joints has clinical feature that resembles those of osteoarthritis, but it has a unique manifestation. We reported a case of a patient of ochronotic arthritis, arthroscopic findings showed large areas of darkly pigmented full-thickness cartilage defects in the right knee, the whole meniscal parenchymatous tissue was also darkly pigmented," wrote B.H. Zhao and colleagues, Hebei Medical University. The researchers concluded: "Histological investigation proved to be ochronosis." Zhao and colleagues published their study in Knee Surgery Sports Traumatology Arthroscopy (Osteoarthritis' Ochronotic arthritis! Knee Surgery Sports Traumatology Arthroscopy, 2009;17(7):778-781). For additional information, contact B.C. Chen, Hebei Medical University, Hospital 3, Dept. of Joint Surgery, 139 Ziqiang Rd., Shijiazhuang 050051, Hebei, People's Republic of China. Publisher contact information for the journal Knee Surgery Sports Traumatology Arthroscopy is: Springer, 233 Spring St., New York, NY 10013, USA. Keywords: People's Republic of China, Shijiazhuang, Alkaptonuria, Arthritis, Arthroscopy, Enzyme Research, Joint Disease, Osteoarthritis, Oxidase, Surgery, Traumatology, Hebei Medical University. This article was prepared by Pain & Central Nervous System Week editors from staff and other reports. Copyright 2009, Pain & Central Nervous System Week via NewsRx.com.
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