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Genetic counseling is the process of providing individuals Alkaptonuria is inherited in an autosomal recessive manner. – ALKAPTONURIA; AKU – HOMOGENTISIC ACID OXIDASE in the homogentisate 1,2-dioxygenase gene (HGD; ) on chromosome 3q Alkaptonuria is a rare inherited genetic disorder in which the body cannot process the amino acids phenylalanine and tyrosine, which occur in protein.

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Effects of ascorbic acid and low-protein diet in alkaptonuria. Human Molecular Genetics 9: No phenotypes other than those discussed in this GeneReview are associated with pathogenic variants in HGD. Affected mice showed high levels of urinary homogentisic acid without signs of ochronosis or arthritis. Oxidation of homogentisic acid HGA excreted in the urine produces a melanin-like product and causes the urine to turn dark on standing. See Molecular Genetics for information on allelic variants detected in this gene.

The HGD enzyme is involved in the metabolism chemical processing of the aromatic amino acids phenylalanine and tyrosine. This accumulation causes thickening of the valves and narrowing stenosis of the openings of the valves.

Rare Disease Database

A spinal x-ray will reveal disk degeneration combined with dense calcification, particularly in the lumbar area. Mutations in brief No. Joint replacement in individuals with alkaptonuria is associated with prosthetic survival comparable to that found in individuals with osteoarthritis [ Spencer et al ]. Dietary restriction low protein diet is beneficial, but compliance is often limited. However, darkening may not occur for several hours after voiding and many henetics never observe any abnormal color to their urine.

Ocular albinism 1 Oculocutaneous albinism Hermansky—Pudlak syndrome Waardenburg syndrome.

Carrier Heterozygote Detection Molecular genetic testing. Connective Tissue and Its Heritable Disorders. Journal of Cellular Physiology Eventually, this discoloration may be apparent on the skin overlying the cartilage. Nitisinone is approved for the treatment of tyrosinemia type I.


With echocardiography, sound waves are bounced off the heart echoesenabling physicians to study cardiac function and motion. First report of a deletion encompassing an entire exon in the homogentisate 1,2-dioxygenase gene causing alkaptonuria. The inability to break down HGA leads to its accumulation. Affected individuals may develop discoloration of the skin overlying cartilage within the body such as over part of the outer ear.

He was found to be compound heterozygous for 2 mutations in the HGD gene: Information on current clinical trials is posted on the Internet at www. A novel therapeutic trial of homogentisic aciduria in a murine model of alkaptonuria. The tyrosine degradation pathway. Journal of Medical Genetics This pigment is able to trigger numerous redox reactions and induce free radical production, causing further damage to the connective tissue.

Rapid detection methods for five HGO gene mutations genwtics alkaptonuria. The HGD gene codes for the enzyme required for the breakdown of homogentisic acid.

Contact for additional information about alkaptonuria: Beltran-Valero de Bernabe, D. GeneReviews staff have not independently verified the classification of variants. Surveillance CT scans according to the recommendation of a cardiologist in affected individuals with coronary artery calcification. Sign up for e-alerts. Alkaptonuria is an autosomal recessive metabolic disorder characterized by accumulation of homogentisic acid, leading to darkened urine, pigmentation of connective tissue ochronosisjoint and spine arthritis, and destruction of the cardiac valves summary by Vilboux et al.

Statistically significant improvement in hip range of motion and measurements of musculoskeletal function were not observed in the treatment group compared to the genrtics group; however there was a positive trend showing slowing of aortic stenosis.

Management of joint pain tailored to the individual; physical and occupational therapy to help maintain muscle strength and flexibility; knee, hip, and shoulder replacements when needed; surgical intervention for prostate stones and renal stones as needed; aortic stenosis may necessitate valve replacement.


Prevalence At least affected individuals have been described in the literature; this is likely an underestimate. They found that joint replacement was performed at a mean age of 55 years and that renal stones developed at 64 years, cardiac-valve involvement genetids 54 years, and alkaptonuia artery calcification at 59 years.

In 2 of the infants studied a 4- and a 5-month-oldascorbic acid may have doubled the amount of homogentisic acid in the urine, presumably through an effect on the immature p-hydroxyphenylpyruvic acid oxidase.

Pigment Cell Melanoma Res. Genetic Counseling Genetic counseling is the process alkaptonurua providing individuals and families with information on the nature, inheritance, and implications of genetic disorders to help them make informed medical and personal decisions.

The amount of HGA excreted per day in individuals with alkaptonuria is usually between one and eight grams. Affected individuals may develop abnormalities affecting the tendons including thickened Achilles tendons venetics inflammation of the tendons tendonitis.

Orphanet: Alkaptonuria

The molecular basis of alkaptonuria. It is appropriate to evaluate apparently asymptomatic older and younger sibs of a proband in order to identify as early as possible those who would benefit from preventive measures.

Free Radical Biology and Medicine 3: The human homogentisate 1,2-dioxygenase HGO gene.

Journal of Cell Physiology Elevated amounts of homogentisic acid in the urine can be detected by gas chromatography-mass spectrometry analysis.

See Quick Reference for an explanation of nomenclature. This assigns scores to the presence of particular symptoms and features, such as the presence of eye and skin pigmentation, joint pain, heart problems, and organ stones.