Beta-Ureidopropionase Deficiency

What else is it called?

  • Beta-alanine synthase deficiency
  • Deficiency of beta-ureidopropionase

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What causes it?

This disorder is caused by a problem in the UPB1 gene. This gene provides instructions for the beta-ureidopropionase enzyme which is involved in the last step of the process of breaking down molecules that are budling blocks of DNA and RNA. We call these molecules pyrimidines.

This process is needed for getting certain acids that protect brain cells from damage caused by toxins, inflammation, and other factors and to send signals between nerve cells and control the level of a chemical messenger called dopamine.

If there is a problem in the UPB1 gene, you will not produce enough or any of the beta-ureidopropionase enzyme at all. Therefore, you will be unable to break down pyrimidines. This may cause neurological problems.

How common is it?

We do not know how many people have this disorder. It is very rare with only a small amount of cases that are known. The prevalence of this disease has been 1 in 6000 in Japan. It is estimated that affected individuals with absent or mild neurological problems may never be diagnosed.

What are the signs and symptoms?

The development of neurological problems and their severity varies depending on the extent of reduction of the beta-ureidopropionase enzyme activity. The onset of the disorder is common during the neonatal and infancy period.

Symptoms and signs may include:

  • Low muscle tone (hypotonia)
  • Seizures
  • Speech difficulties
  • Developmental delay
  • Intellectual disability
  • Autistic behaviors that affect communication and social interaction
  • Abnormally small head size (microcephaly)
  • Brain abnormalities
  • Vision impairment that may lead to vision loss

How is it diagnosed?

You will be diagnosed after a clinical examination by your specialist or doctor. However, as the signs and symptoms of this disorder are similar to other conditions, you will need further tests. Doctors will analyse your blood and urine using a special test. You may not have any neurological problems so you can only be diagnosed by laboratory testing. Follow-up testing may include MRI and EEG.

Can it be treated?

Unfortunately, there is no cure for this disorder. Therefore, treatment is focused on managing individual symptoms and providing comfort and relief in the form of supporting the individual and any family members. A multi-disciplinary team of specialists and support networks will be involved in the management of the condition and to offer practical and emotional support.

Do my family need to be tested?

Beta-Ureidopropionase deficiency can only be passed on to a child if both parents have a copy of the faulty gene. This is called autosomal recessive inheritance. A person who has a copy of the faulty gene is known as a carrier.

If both parents are carriers, their child has a one in four (25%) chance of inheriting the disorder, and a one in two chance (50%) of being a carrier. This is the same for each child the parents have.

If the child only inherits one copy of the faulty gene, they will be a carrier but will not have the disorder. In some rare cases, carriers have had mild symptoms of the disorder for which they carry the faulty gene.

Once you are diagnosed, you can speak to a genetic counsellor. They can explain how you may have inherited Beta-Ureidopropionase deficiency. They can also tell you about genetic testing for the rest of your family. They can provide advice and support if you go on to have children of your own.

Diagram showing the autosomal recessive inheritance pattern.

Relevant Organisations


References are available on request. Please contact us by phoning 0845 241 2173 or emailing [Resource Library No: AAP002]

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