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Homocystinuria due to Cystathionine Beta-Synthase Deficiency
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NORD is very grateful to Jan P. Kraus, PhD, Professor of Pediatrics, University of Colorado, for assistance in the preparation of this report.
Synonyms of Homocystinuria due to Cystathionine Beta-Synthase Deficiency
- Classical Homocystinuria
- cystathionine beta-synthase deficiency
- 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). Infants who develop homocystinuria due to CBS deficiency (which is also known as classical 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). In addition, affected individuals may be at risk for the development of blood clots that can become lodged within certain large and small blood vessels (thromboembolisms), potentially leading to life-threatening complications. Homocystinuria due to deficiency of CBS deficiency is inherited as an autosomal recessive trait. The disorder is caused by changes (mutations) of a gene on the long arm (q) of chromosome 21 (21q22.3) that regulates the production of the CBS enzyme.
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Organizations related to Homocystinuria due to Cystathionine Beta-Synthase Deficiency
- Arc
1660 L Street, NW, Suite 301
Washington DC 20036
Phone #: 202-534-3700
800 #: 800-433-5255
e-mail: info@thearc.org
Home page: http://www.thearc.org
- 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 #: 084-5 2-41 2174
800 #: 080-0 6-52 3181
e-mail: info.svcs@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 #: 301-251-4925
800 #: 888-205-2311
e-mail: http://rarediseases.info.nih.gov/GARD/EmailForm.aspx
Home page: http://rarediseases.info.nih.gov/GARD
- 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 #: 914-997-4488
800 #: 888-663-4637
e-mail: Askus@marchofdimes.com
Home page: http://www.marchofdimes.com
- National Institute of Neurological Disorders and Stroke (NINDS)
P.O. Box 5801
Bethesda MD 20824
Phone #: 301-496-5751
800 #: 800-352-9424
e-mail: me20t@nih.gov
Home page: http://www.ninds.nih.gov/
- Save Babies Through Screening Foundation
P.O. Box 42197
Cincinnati OH 45242
Phone #: 610-251-9876
800 #: 888-454-3383
e-mail: emails@savebabies.org
Home page: http://www.savebabies.org
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