$Unique_ID{BRK03829} $Pretitle{} $Title{Homocystinuria} $Subject{Homocystinuria Homocystinemia Cystathioninuria Marfan Syndrome } $Volume{} $Log{} Copyright (C) 1987, 1988, 1990 National Organization for Rare Disorders, Inc. 463: Homocystinuria ** IMPORTANT ** It is possible the main title of the article (Homocystinuria) is not the name you expected. Please check the SYNONYMS listing on the next page to find alternate names, disorder subdivisions, and related disorders covered by this article. Synonyms Homocystinemia Information on the following disorders can be found in the Related Disorders section of this report: Cystathioninuria Marfan Syndrome General Discussion ** REMINDER ** The information contained in the Rare Disease Database is provided for educational purposes only. It should not be used for diagnostic or treatment purposes. If you wish to obtain more information about this disorder, please contact your personal physician and/or the agencies listed in the "Resources" section of this report. Homocystinuria is a rare hereditary error of metabolism. The amino acid methionine is not properly metabolized due to a defect in the enzyme cystathionine synthetase. Symptoms Homocystinuria is a genetic disorder characterized by mental retardation, dislocated lenses, sparse hair, chronic flushing of the face (malar flush), and relaxation of ligaments. Patients may exhibit the symptoms of Marfan Syndrome. This hereditary connective tissue disorder is characterized by an elongated body, long, thin arms and legs, spiderlike hands and fingers, cardiovascular defects, and depression of the breast bone (pectus excavatum). The enzyme cystathionine synthetase is deficient in homocystinuria. The amino acids homocystine and methionine are elevated in the blood plasma, cerebro-spinal fluid and urine. The lenses of one or both eyes, may be out of their normal position (ectopic), fibers of the lens may degenerate, and zonal cataracts are possible. Porous bones (Osteoporosis) may also occur. The walls of the blood vessels may show degeneration. Blood clots (thromboemboli) may block the blood flow, possibly in the lung vessels (pulmonary embolism), or in the blood vessels feeding the heart muscle (coronary occlusion). These conditions may be life-threatening. (For more information on cataracts, choose "cataracts" as your search term in the Rare Disease Database; for more information on Osteoporosis, see the articles in the Prevalent Health Conditions/Concerns area of NORD Services.) Causes Homocystinuria is a genetic disorder inherited through autosomal recessive genes. Symptoms are caused by an inborn error of amino acid metabolism resulting from deficiency of the enzyme cystathionine synthetase, responsible for synthesis of the amino acid cystathionine. Human traits including the classic genetic diseases, are the product of the interaction of two genes for that condition, one received from the father and one from the mother. In recessive disorders, the condition does not appear unless a person inherits the same defective gene from each parent. If one receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will show no symptoms. The risk of transmitting the disease to the children of a couple, both of whom are carriers for a recessive disorder, is twenty-five percent. Fifty percent of their children will be carriers, but healthy as described above. Twenty-five percent of their children will receive both normal genes, one from each parent and will be genetically normal. Affected Population Homocystinuria starts at birth. Males and females are affected in equal numbers. Like other inborn errors of metabolism, it is a very rare disorder. Related Disorders Cystathioninuria is a genetic disorder transmitted through autosomal recessive genes. It is caused by an inborn error of metabolism, cystathionase. An excessive amount of cystathionine in the urine can be identified by tests. Mental retardation sometimes also occurs. Marfan Syndrome is a genetic disorder of connective tissue. It primarily affects the bones and ligaments, the eyes, the cardiovascular system, and the lungs. Persons with Marfan Syndrome will be tall, slender, and somewhat loose-jointed. The arms, legs, and fingers may be disproportionately long. (For more information on this disorder, choose "Marfan" as your search term in the Rare Disease Database.) Therapies: Standard Treatment for Homocystinuria consists in controlled supplemental intake of the amino acids methionine, cystine, and folic acid. Massive doses of pyridoxine (a form of Vitamin B6) may also be prescribed. Genetic counseling will be helpful for families of children with Homocystinuria. Therapies: Investigational In patients with Homocystinuria who are also affected by reduced activity of the enzyme methionine synthase, experimental treatment with Vitamin B-12 is being tested. More research is needed to determine effectiveness of this treatment. This disease entry is based upon medical information available through March 1990. Since NORD's resources are limited, it is not possible to keep every entry in the Rare Disease Database completely current and accurate. Please check with the agencies listed in the Resources section for the most current information about this disorder. Resources For more information on Homocystinuria, please contact: National Organization for Rare Disorders (NORD) P.O. Box 8923 New Fairfield, CT 06812-1783 (203) 746-6518 National Digestive Diseases Information Clearinghouse Box NDDIC Bethesda, MD 20892 (301) 468-6344 For information on genetics and genetic counseling referrals, please contact: March of Dimes Birth Defects Foundation 1275 Mamaroneck Avenue White Plains, NY 10605 (914) 428-7100 Alliance of Genetic Support Groups 35 Wisconsin Circle, Suite 440 Chevy Chase, MD 20815 (800) 336-GENE (301) 652-5553 References THE METABOLIC BASIS OF INHERITED DISEASE, 5th ed.,: John B. Stanbury, et al., eds.; McGraw Hill, 1983.