Diseases & Conditions


A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Homocystinuria


Synonyms of Homocystinuria
  • No synonyms found

Disorder Subdivisions

  • No synonyms found


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
    Crewe Intl CW2 6BG
    Phone #: +44- 87-0 7700 325
    800 #: --
    e-mail: info@climb.org.uk
    Home page: http://www.CLIMB.org.uk
  • 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
    Silver Spring MD 20910
    Phone #: 301-565-3842
    800 #: 800-433-5255
    e-mail: info@thearc.org
    Home page: http://www.thearc.org/



For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders, Inc. ? (NORD). A copy of the complete report can be obtained for a small fee by visiting the NORD website. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational treatments (if available), and references from medical literature. For a full-text version of this topic, see http://www.rarediseases.org/search/rdblist.html