BACK TOTOP Browse A-ZSearchBrowse A-ZABCDEFGHIJKLMNOPQRSTUVWXYZ0-9 E-mail FormEmail ResultsName:Email address:Recipients Name:Recipients address:Message: Print-FriendlyBookmarksbookmarks-menuHomocystinuriaCystathionine beta-synthase deficiency; CBS deficiency; HCYHomocystinuria is a genetic disorder that affects the metabolism of the amino acid methionine. Amino acids are the building blocks of life.MetabolismMetabolism refers to all the physical and chemical processes in the body that convert or use energy, such as:BreathingCirculating bloodControlling bo...ImageRead Article Now Book Mark Article Amino acidAmino acids are molecules that combine to form proteins. Amino acids and proteins are the building blocks of life. When proteins are digested or bro...ImageRead Article Now Book Mark Article Causes Homocystinuria is inherited in families as an autosomal recessive trait. This means that the child must inherit a non-working copy of the gene from each parent to be seriously affected.Autosomal recessiveAutosomal recessive is one of several ways that a trait, disorder, or disease can be passed down through families. An autosomal recessive disorder me...ImageRead Article Now Book Mark Article Homocystinuria has several features in common with Marfan syndrome, including skeletal and eye changes.Marfan syndromeMarfan syndrome is a disorder of connective tissue. This is the tissue that strengthens the body's structures. Disorders of connective tissue affect...ImageRead Article Now Book Mark Article Symptoms Newborn infants appear healthy. Early symptoms, if present, are not obvious.Symptoms may occur as mildly delayed development or failure to thrive. Increasing visual problems may lead to diagnosis of this condition.Failure to thriveFailure to thrive refers to children whose current weight or rate of weight gain is much lower than that of other children of similar age and sex....Read Article Now Book Mark Article Visual problemsThere are many types of eye problems and vision disturbances, such as: Halos Blurred vision (the loss of sharpness of vision and the inability to see...ImageRead Article Now Book Mark Article Other symptoms include:Chest deformities (pectus carinatum, pectus excavatum) Pectus carinatumPectus carinatum is present when the chest protrudes over the sternum. It is often described as giving the person a bird-like appearance.ImageRead Article Now Book Mark Article Pectus excavatumPectus excavatum is a medical term that describes an abnormal formation of the rib cage that gives the chest a caved-in or sunken appearance....ImageRead Article Now Book Mark Article Flush across the cheeks High arches of the feet High arches of the feetHigh arch is a foot arch that is raised more than normal. The arch runs from the toes to the heel on the bottom of the foot. It is also called pes ...Read Article Now Book Mark Article Intellectual disability Knock knees Knock kneesKnock knees are condition in which the knees touch, but the ankles do not touch. The legs turn inward.Read Article Now Book Mark Article Long limbs Mental disorders Nearsightedness Spidery fingers (arachnodactyly) ArachnodactylyArachnodactyly is a condition in which the fingers are long, slender, and curved. They look like the legs of a spider (arachnid).Read Article Now Book Mark Article Tall, thin build Exams and Tests The health care provider may notice that the child is tall and thin.Other signs include:Curved spine (scoliosis) ScoliosisScoliosis is an abnormal curving of the spine. Your spine is your backbone. It runs straight down your back. Everyone's spine naturally curves a b...ImageRead Article Now Book Mark Article Deformity of the chest Dislocated lens of the eye If there is poor or double vision, an eye doctor (ophthalmologist) will perform a dilated eye exam to look for dislocation of the lens or nearsightedness.There may be a history of blood clots. Intellectual disability or mental illness is also possible.Tests that may be ordered include any of the following:Amino acid screen of blood and urine Genetic testing Homocysteine level Liver biopsy and enzyme assay Liver biopsyA liver biopsy is a test that takes a sample of tissue from the liver for examination.ImageRead Article Now Book Mark Article Enzyme assayELISA stands for enzyme-linked immunoassay. It is a commonly used laboratory test to detect antibodies in the blood. An antibody is a protein produ...ImageRead Article Now Book Mark Article Skeletal x-ray x-rayX-rays are a type of electromagnetic radiation, just like visible light. An x-ray machine sends individual x-ray waves through the body. The images...ImageRead Article Now Book Mark Article Skin biopsy with a fibroblast culture Skin biopsyA skin lesion biopsy is when a small amount of skin is removed so it can be examined under a microscope. The skin is tested to look for skin conditi...ImageRead Article Now Book Mark Article Standard ophthalmic examStandard ophthalmic examA standard eye exam is a series of tests done to check your vision and the health of your eyes.ImageRead Article Now Book Mark Article Treatment There is no cure for homocystinuria. About half of people with the disease respond to vitamin B6 (also known as pyridoxine). Vitamin B6Vitamin B6 is a water-soluble vitamin. Water-soluble vitamins dissolve in water so the body cannot store them. Leftover amounts of the vitamin leav...ImageRead Article Now Book Mark Article Those who do respond will need to take vitamin B6, B9 (folate), and B12 supplements for the rest of their lives. Those who do not respond to supplements will need to eat a low-methionine diet. Most will need to be treated with trimethylglycine (a medicine also known as betaine).Neither a low-methionine diet nor medicine will improve existing intellectual disability. Medicine and diet should be closely monitored by a doctor who has experience treating homocystinuria. Support Groups More information and support for people with homocystinuria and their families can be found at:National Organization for Rare Disorders -- rarediseases.org/rare-diseases/homocystinuria-due-to-cystathionine-beta-synthase-deficiency/ HCU Network America -- hcunetworkamerica.org Outlook (Prognosis) Although no cure exists for homocystinuria, vitamin B therapy can help about half of people affected by the condition.If the diagnosis is made in childhood, starting a low-methionine diet quickly may prevent some intellectual disability and other complications of the disease. For this reason, some states screen for homocystinuria in all newborns.People whose blood homocysteine levels continue to rise are at increased risk for blood clots. Clots can cause serious medical problems and shorten lifespan. Possible Complications Most serious complications occur due to blood clots. These episodes can be life threatening.Dislocated lenses of the eyes can seriously damage vision. Lens replacement surgery may be needed.Intellectual disability is a serious outcome of the disease. But, it can be reduced if diagnosed early. When to Contact a Medical Professional Contact your provider if you or a family member shows symptoms of this disorder, especially if you have a family history of homocystinuria. Prevention Genetic counseling is recommended for people with a family history of homocystinuria who want to have children. Prenatal diagnosis of homocystinuria is available. This involves culturing amniotic cells or chorionic villi to test for cystathionine synthase (the enzyme that is missing in homocystinuria).If there are known gene defects in the parents or family, samples from chorionic villus sampling or amniocentesis can be used to test for these defects.Chorionic villus samplingChorionic villus sampling (CVS) is a test some pregnant women have to screen their baby for genetic problems.ImageRead Article Now Book Mark Article AmniocentesisAmniocentesis is a test that can be done during pregnancy to look for certain problems in the developing baby. These problems include:Birth defectsG...ImageRead Article Now Book Mark Article Open ReferencesReferencesSchiff M, Blom H. Homocystinuria and hyperhomocysteinemia. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 198.Shchelochkov OA, Venditti CP. Methionine. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 103.3.AllVideoImagesTogPectus excavatum - illustration Pectus excavatum is a condition in which the breast bone (sternum) appears sunken and the chest concave. It is sometimes called funnel chest. The majority of these cases are not associated with any other condition (isolated findings). However, some genetic conditions include pectus excavatum.Pectus excavatumillustrationPectus excavatum - illustration Pectus excavatum is a condition in which the breast bone (sternum) appears sunken and the chest concave. It is sometimes called funnel chest. The majority of these cases are not associated with any other condition (isolated findings). However, some genetic conditions include pectus excavatum.Pectus excavatumillustrationRelated Information Metabolism(Special Topic)Autosomal recessive(Special Topic)Nearsightedness(Condition)Dislocation(Injury)Blood clots(Condition)Failure to thrive(Condition)Vision problems(Symptoms)Intellectual disability(Condition)Marfan syndrome(Condition)Arachnodactyly(Symptoms)Scoliosis - InDepth(In-Depth) Review Date: 11/1/2021 Reviewed By: Anna C. Edens Hurst, MD, MS, Associate Professor in Medical Genetics, The University of Alabama at Birmingham, Birmingham, AL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. 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HomocystinuriaCystathionine beta-synthase deficiency; CBS deficiency; HCYHomocystinuria is a genetic disorder that affects the metabolism of the amino acid methionine. Amino acids are the building blocks of life.MetabolismMetabolism refers to all the physical and chemical processes in the body that convert or use energy, such as:BreathingCirculating bloodControlling bo...ImageRead Article Now Book Mark Article Amino acidAmino acids are molecules that combine to form proteins. Amino acids and proteins are the building blocks of life. When proteins are digested or bro...ImageRead Article Now Book Mark Article Causes Homocystinuria is inherited in families as an autosomal recessive trait. This means that the child must inherit a non-working copy of the gene from each parent to be seriously affected.Autosomal recessiveAutosomal recessive is one of several ways that a trait, disorder, or disease can be passed down through families. An autosomal recessive disorder me...ImageRead Article Now Book Mark Article Homocystinuria has several features in common with Marfan syndrome, including skeletal and eye changes.Marfan syndromeMarfan syndrome is a disorder of connective tissue. This is the tissue that strengthens the body's structures. Disorders of connective tissue affect...ImageRead Article Now Book Mark Article Symptoms Newborn infants appear healthy. Early symptoms, if present, are not obvious.Symptoms may occur as mildly delayed development or failure to thrive. Increasing visual problems may lead to diagnosis of this condition.Failure to thriveFailure to thrive refers to children whose current weight or rate of weight gain is much lower than that of other children of similar age and sex....Read Article Now Book Mark Article Visual problemsThere are many types of eye problems and vision disturbances, such as: Halos Blurred vision (the loss of sharpness of vision and the inability to see...ImageRead Article Now Book Mark Article Other symptoms include:Chest deformities (pectus carinatum, pectus excavatum) Pectus carinatumPectus carinatum is present when the chest protrudes over the sternum. It is often described as giving the person a bird-like appearance.ImageRead Article Now Book Mark Article Pectus excavatumPectus excavatum is a medical term that describes an abnormal formation of the rib cage that gives the chest a caved-in or sunken appearance....ImageRead Article Now Book Mark Article Flush across the cheeks High arches of the feet High arches of the feetHigh arch is a foot arch that is raised more than normal. The arch runs from the toes to the heel on the bottom of the foot. It is also called pes ...Read Article Now Book Mark Article Intellectual disability Knock knees Knock kneesKnock knees are condition in which the knees touch, but the ankles do not touch. The legs turn inward.Read Article Now Book Mark Article Long limbs Mental disorders Nearsightedness Spidery fingers (arachnodactyly) ArachnodactylyArachnodactyly is a condition in which the fingers are long, slender, and curved. They look like the legs of a spider (arachnid).Read Article Now Book Mark Article Tall, thin build Exams and Tests The health care provider may notice that the child is tall and thin.Other signs include:Curved spine (scoliosis) ScoliosisScoliosis is an abnormal curving of the spine. Your spine is your backbone. It runs straight down your back. Everyone's spine naturally curves a b...ImageRead Article Now Book Mark Article Deformity of the chest Dislocated lens of the eye If there is poor or double vision, an eye doctor (ophthalmologist) will perform a dilated eye exam to look for dislocation of the lens or nearsightedness.There may be a history of blood clots. Intellectual disability or mental illness is also possible.Tests that may be ordered include any of the following:Amino acid screen of blood and urine Genetic testing Homocysteine level Liver biopsy and enzyme assay Liver biopsyA liver biopsy is a test that takes a sample of tissue from the liver for examination.ImageRead Article Now Book Mark Article Enzyme assayELISA stands for enzyme-linked immunoassay. It is a commonly used laboratory test to detect antibodies in the blood. An antibody is a protein produ...ImageRead Article Now Book Mark Article Skeletal x-ray x-rayX-rays are a type of electromagnetic radiation, just like visible light. An x-ray machine sends individual x-ray waves through the body. The images...ImageRead Article Now Book Mark Article Skin biopsy with a fibroblast culture Skin biopsyA skin lesion biopsy is when a small amount of skin is removed so it can be examined under a microscope. The skin is tested to look for skin conditi...ImageRead Article Now Book Mark Article Standard ophthalmic examStandard ophthalmic examA standard eye exam is a series of tests done to check your vision and the health of your eyes.ImageRead Article Now Book Mark Article Treatment There is no cure for homocystinuria. About half of people with the disease respond to vitamin B6 (also known as pyridoxine). Vitamin B6Vitamin B6 is a water-soluble vitamin. Water-soluble vitamins dissolve in water so the body cannot store them. Leftover amounts of the vitamin leav...ImageRead Article Now Book Mark Article Those who do respond will need to take vitamin B6, B9 (folate), and B12 supplements for the rest of their lives. Those who do not respond to supplements will need to eat a low-methionine diet. Most will need to be treated with trimethylglycine (a medicine also known as betaine).Neither a low-methionine diet nor medicine will improve existing intellectual disability. Medicine and diet should be closely monitored by a doctor who has experience treating homocystinuria. Support Groups More information and support for people with homocystinuria and their families can be found at:National Organization for Rare Disorders -- rarediseases.org/rare-diseases/homocystinuria-due-to-cystathionine-beta-synthase-deficiency/ HCU Network America -- hcunetworkamerica.org Outlook (Prognosis) Although no cure exists for homocystinuria, vitamin B therapy can help about half of people affected by the condition.If the diagnosis is made in childhood, starting a low-methionine diet quickly may prevent some intellectual disability and other complications of the disease. For this reason, some states screen for homocystinuria in all newborns.People whose blood homocysteine levels continue to rise are at increased risk for blood clots. Clots can cause serious medical problems and shorten lifespan. Possible Complications Most serious complications occur due to blood clots. These episodes can be life threatening.Dislocated lenses of the eyes can seriously damage vision. Lens replacement surgery may be needed.Intellectual disability is a serious outcome of the disease. But, it can be reduced if diagnosed early. When to Contact a Medical Professional Contact your provider if you or a family member shows symptoms of this disorder, especially if you have a family history of homocystinuria. Prevention Genetic counseling is recommended for people with a family history of homocystinuria who want to have children. Prenatal diagnosis of homocystinuria is available. This involves culturing amniotic cells or chorionic villi to test for cystathionine synthase (the enzyme that is missing in homocystinuria).If there are known gene defects in the parents or family, samples from chorionic villus sampling or amniocentesis can be used to test for these defects.Chorionic villus samplingChorionic villus sampling (CVS) is a test some pregnant women have to screen their baby for genetic problems.ImageRead Article Now Book Mark Article AmniocentesisAmniocentesis is a test that can be done during pregnancy to look for certain problems in the developing baby. These problems include:Birth defectsG...ImageRead Article Now Book Mark Article Open ReferencesReferencesSchiff M, Blom H. Homocystinuria and hyperhomocysteinemia. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 198.Shchelochkov OA, Venditti CP. Methionine. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 103.3.