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Aug 16, 2023

Homocystinuria: Vitamin Deficiency Signs in Children

Homocystinuria is a medical condition in which the body does not break down certain proteins into amino acids. This results in vitamin deficiencies, vision changes, blood clots, learning disabilities,

Homocystinuria is a medical condition in which the body does not break down certain proteins into amino acids. This results in vitamin deficiencies, vision changes, blood clots, learning disabilities, poor weight gain, and poor growth in children.

This article will discuss dietary changes and vitamin supplements for those with homocystinuria.

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The signs and symptoms of homocystinuria vary widely from person to person. Generally, signs of the condition will start before the infant is 1 year old.

People who are only mildly affected by homocystinuria may not have signs or symptoms until adulthood.

The symptoms of homocystinuria include:

When someone with homocystinuria is diagnosed and treated promptly their symptoms are more likely to remain mild. Whereas, someone with the condition who does not receive treatment is more apt to develop issues relating to the condition.

People who have the form of homocystinuria that responds to vitamin B6 treatment tend to have a more mild form of the condition compared to those who do not respond to B6 treatment.

Gene mutations cause homocystinuria. Mutations of the cystathionine beta-synthase (CBS) gene are the most common cause of homocystinuria.

Other genetic causes of homocystinuria include MTHFR, MTR, MTRR, and MMADHC mutations.

Homocystinuria is a condition that is passed down from parents to their children. It is an autosomal recessive condition, meaning that both parents must have the CBS gene mutation for the child to get the condition.

The CBS gene tells the body how to make an enzyme called cystathionine beta-synthase. This enzyme breaks down the amino acid methionine. When the CBS gene is not working properly, the body cannot use the amino acid homocysteine. This results in an excess of homocysteine and methionine in the blood.

A common misconception about homocystinuria is that a vitamin deficiency causes it. While vitamin deficiencies result from homocystinuria, the condition is caused by genetic mutations.

If you have homocystinuria, you are unable to make the CBS enzyme. This enzyme uses vitamin B6 to change homocysteine into other necessary amino acids. As a result, you will need vitamin B6 and other vitamin supplements.

A blood test is necessary to diagnose homocystinuria. Newborns receive the newborn screening after birth, which tests for homocystinuria, among other conditions.

The blood test measures how much methionine and homocysteine are in the blood. An out-of-range test result does not diagnose homocystinuria. The healthcare provider will follow up with additional blood tests and genetic testing to confirm a diagnosis.

A false-positive result, in which the test inaccurately indicates the condition, is rare but can happen if the infant was born prematurely or received liquid nutrition intravenously, such as with total perenteral nutrition (TPN). A false-negative result, indicating the condition is present when it is not, can occur if the test is given before the baby is 24 hours old.

People diagnosed with homocystinuria and not responsive to vitamin B6 supplementation will need to implement a low-protein and low-methionine diet.

Low-methionine foods are typically vegan. They include:

A low-protein diet restricts the amount of animal and nonanimal protein a person eats. The amount of protein allotted will vary from person to person and should be set by a registered dietitian and a healthcare provider.

About 50% of people with homocystinuria will respond to treatment with vitamin B6 supplements. These people will also need to take vitamin B9 (folate) and B12 for their entire life.

The other 50% not responding to vitamin supplementation will need to make diet modifications and take betaine, a medicine used to treat homocystinuria.

Homocystinuria can cause serious complications if treatment is delayed. Healthcare providers will treat complications based on symptoms and the severity of the event.

Blood clots are one of the most serious complications of homocystinuria. Treatment will depend on where the blood clot is located.

Another complication is the dislocation of the eye lens. Treatment involves lens replacement surgery.

One of the best sources of support for parents with a child who has homocystinuria is a genetic counselor or medical geneticist. These healthcare providers help families learn about their child's condition and the chances of having additional children with homocystinuria.

Support can also come from social workers and local support groups. These resources can guide parents through tough times and help them find support within their community.

Homocystinuria is an inherited condition passed down by parents to their children. It causes symptoms like learning disabilities, poor growth, and blood clots. If quickly diagnosed and treatment is prompt, there generally are good outcomes. People with the condition will need lifelong treatment with vitamin supplements and diet changes.

Health Resources & Services Administration. Homocystinuria.

MedlinePlus. Homocystinuria.

National Organization for Rare Disorders. Homocystinuria due to cystathionine beta-synthase deficiency.

Texas Children's. Methionine food list.

Mount Sinai. Homocystinuria.

By Patty Weasler, RN, BSNPatty is a registered nurse with over a decade of experience in pediatric critical care. Her passion is writing health and wellness content that anyone can understand and use.