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Copyright 1987, 1988, 1990, 1994, 1995, 1996, 1997, 1998, 1999, 2000
Synonyms of Homocystinuria
Disorder Subdivisions
General Discussion
Homocystinuria is a rare metabolic condition characterized by an excess of the compound homocystine in the urine. The condition may result from deficiency of any of several enzymes involved in the conversion of the essential amino acid methionine to another amino acid (cysteine)--or, less commonly, impaired conversion of the compound homocysteine to methionine. Enzymes are proteins that accelerate the rate of chemical reactions in the body. Certain amino acids, which are the chemical building blocks of proteins, are essential for proper growth and development.
In most cases, Homocystinuria is caused by reduced activity of an enzyme known as cystathionine beta-synthase (CBS). Due to deficiency of the CBS enzyme, infants with Homocystinuria may fail to grow and gain weight at the expected rate (failure to thrive) and have developmental delays. By approximately age three, additional, more specific symptoms and findings may become apparent. These may include partial dislocation (subluxation) of the lens of the eyes (ectopia lentis), associated "quivering" (iridodonesis) of the colored region of the eyes (iris), severe nearsightedness (myopia), and other eye (ocular) abnormalities. Although intelligence may be normal in some cases, many children may be affected by progressive mental retardation. In addition, some may develop psychiatric disturbances and/or episodes of uncontrolled electrical activity in the brain (seizures). Affected individuals also tend to be thin with unusually tall stature; long, slender fingers and toes (arachnodactyly); and elongated arms and legs ("marfanoid" features). Additional skeletal abnormalities may include progressive sideways curvature of the spine (scoliosis), abnormal protrusion or depression of the breastbone (pectus carinatum or excavatum), and generalized loss of bone density (osteoporosis). In addition, in those with the disorder, blood clots may tend to develop or become lodged within certain large and small blood vessels (thromboembolisms), potentially leading to life-threatening complications.
Homocystinuria due to deficiency of cystathionine synthase is inherited as an autosomal recessive trait. The disorder results from changes (mutations) of a gene on the long arm (q) of chromosome 21 (21q22.3) that regulates the production of the CBS enzyme.
Organizations related to Homocystinuria
- Belgian Association for Metabolic Diseases (BOKS)
Alice Nahonlann 7
Melsele None 9120
Phone #: 323-775-4839
800 #: N/A
e-mail: info@boks.be
Home page: http://www.boks.be
- CLIMB (Children Living with Inherited Metabolic Diseases)
Climb Building
176 Nantwich Road
Crewe Intl CW2 6BG
Phone #: +44- 87-0 7700 325
800 #: --
e-mail: info@climb.org.uk
Home page: http://www.CLIMB.org.uk
- Genetic and Rare Diseases (GARD) Information Center
PO Box 8126
Gaithersburg MD 20898-8126
Phone #: 301-519-3194
800 #: 888-205-2311
e-mail: gardinfo@nih.gov
Home page: http://www.genome.gov/10000409
- Madisons Foundation
PO Box 241956
Los Angeles CA 90024
Phone #: 310-264-0826
800 #: N/A
e-mail: getinfo@madisonsfoundation.org
Home page: http://www.madisonsfoundation.org
- March of Dimes Birth Defects Foundation
1275 Mamaroneck Avenue
White Plains NY 10605
Phone #: 914-428-7100
800 #: 888-663-4637
e-mail: Askus@marchofdimes.com
Home page: http://www.marchofdimes.com
- NIH/National Digestive Diseases Information Clearinghouse
2 Information Way
Bethesda MD 20892-3570
Phone #: 301-654-3810
800 #: 800-891-5389
e-mail: nddic@info.niddk.nih.gov
Home page: http://www.niddk.nih.gov
- The Arc (a national organization on mental retardation)
1010 Wayne Ave
Suite 650
Silver Spring MD 20910
Phone #: 301-565-3842
800 #: 800-433-5255
e-mail: info@thearc.org
Home page: http://www.thearc.org/
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