Learn About Homocystinuria

What is the definition of Homocystinuria?

Homocystinuria is a genetic disorder that affects the metabolism of the amino acid methionine. Amino acids are the building blocks of all proteins in the body.

What are the alternative names for Homocystinuria?

Cystathionine beta-synthase deficiency; CBS deficiency; HCY

What are the causes of Homocystinuria?

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.

People with homocystinuria have several physical features in common with Marfan syndrome, including skeletal and eye changes.

What are the symptoms of Homocystinuria?

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.

Other symptoms include:

  • Chest deformities (pectus carinatum, pectus excavatum)
  • Flush across the cheeks
  • High arches of the feet
  • Intellectual disability
  • Knock knees
  • Long limbs
  • Mental disorders
  • Nearsightedness
  • Spidery fingers (arachnodactyly)
  • Tall, thin build
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What are the current treatments for Homocystinuria?

There is no cure for homocystinuria. About half of people with the disease respond to vitamin B6 (also known as pyridoxine).

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.

Who are the top Homocystinuria Local Doctors?
Elite in Homocystinuria
Elite in Homocystinuria
Prague, PR, CZ 

Viktor Kozich practices in Prague, Czech Republic. Kozich and is rated as an Elite expert by MediFind in the treatment of Homocystinuria. His top areas of expertise are Homocystinuria, Homocystinuria due to MTHFR Deficiency, Carnitine Palmitoyltransferase 1 Deficiency, and Molybdenum Cofactor Deficiency (MoCD).

Elite in Homocystinuria
Medical Genetics
Elite in Homocystinuria
Medical Genetics
9000 Rockville Pike National Institutes Of Health, Building 49 Rm 4a18, 
Bethesda, MD 
Languages Spoken:
English

Charles Venditti is a Medical Genetics provider in Bethesda, Maryland. Dr. Venditti and is rated as an Elite provider by MediFind in the treatment of Homocystinuria. His top areas of expertise are Methylmalonic Acidemia, Propionic Acidemia, Homocystinuria, and Niemann-Pick Disease.

 
 
 
 
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Elite in Homocystinuria
Elite in Homocystinuria
Rotterdam, ZH, NL 

Henk Blom practices in Rotterdam, Netherlands. Blom and is rated as an Elite expert by MediFind in the treatment of Homocystinuria. Their top areas of expertise are Homocystinuria, Hypermethioninemia, Homocystinuria due to MTHFR Deficiency, and Biotinidase Deficiency.

What are the support groups for Homocystinuria?

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
What is the outlook (prognosis) for Homocystinuria?

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.

What are the possible complications of Homocystinuria?

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 should I contact a medical professional for Homocystinuria?

Contact your provider if you or a family member shows symptoms of this disorder, especially if you have a family history of homocystinuria.

How do I prevent Homocystinuria?

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 conditions in the parents or family, samples from chorionic villus sampling or amniocentesis can be used to test for these defects before a baby is born.

What are the latest Homocystinuria Clinical Trials?
Development and Validation of a Standardized Assessment Instrument for Health-related Quality of Life (HrQoL) in Patients With Classical Homocystinuria

Summary: Patients, parents of young / handicapped patients, and experts will be interviewed to collect contents relevant for HrQoL in CBS deficiency. Based on these data, a questionnaire will be developed and tested for comprehensibility in patients and parents of young / handicapped patients. A final questionnaire version will be tested for psychometric criteria including validity and reliability.

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Clinical and Basic Investigations of Methylmalonic Acidemia (MMA) and Related Disorders

Summary: Methylmalonic acidemia (MMA), one of the most common inborn errors of organic acid metabolism, is heterogeneous in etiology and clinical manifestations. Affected patients with cblA, cblB and mut classes of MMA are medically fragile and can suffer from complications such as metabolic stroke or infarction of the basal ganglia, pancreatitis, end stage renal failure, growth impairment, osteoporosis, a...

Who are the sources who wrote this article ?

Published Date: December 31, 2023
Published 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 C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

What are the references for this article ?

Schiff M, Blom HJ. Homocystinuria and hyperhomocysteinemia. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 193.

Shchelochkov OA, Venditti CP. Methionine./Defects in metabolism of amino acids. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 105.1.