What else is it called?

  • Gamma-Cystathionase Deficiency
  • Cystathionine Gamma-lyase Deficiency Syndrome
  • Cystathionase deficiency

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What causes it?

This disorder is caused by a problem in the CTH gene. This gene provides the instructions for Cystathionine Gamma-Lyase enzyme which helps convert cystathionine to cysteine. Cysteine is used in maintaining the structure of proteins in the body.

If you have a problem in the CTH gene, you will not produce enough of the Cystathionine Gamma-Lyase enzyme. Therefore, Cystathionine will not be converted and will begin to build up inside the body.

There are two types of Cystathioninuria:

  • Primary Cystathioninuria is an inborn error of methionine metabolism, where the conversion of Cystathionine to Cysteine is missing the Cystathionine Gamma-Lyase enzyme
  • Secondary Cystathioninuria results from a Vitamin B6 deficiency and is a side effect of disorders like Neuroblastoma, Argentasffinoma, Hepatoblastoma and after administration of Thyroxine

How common is it?

It is estimated that 1-9 in 100,000 people have Cystathioninuria. It affects both genders equally and does not discriminate between race/ethnic groups.

What are the signs and symptoms?

Cystathioninuria has the same symptoms regardless of whether it is the primary or secondary form of the disorder. There is no specific age for symptom onset.

The general symptoms are as follows;

  • High levels of Cystathionine in the Urine (Cystathioninuria)
  • High levels of Cystathionine in the Blood Plasma (Cystathionemia)
  • Increased urinary excretion

The following symptoms are less common;

  • Mental deficiency
  • Seizures
  • External ear malformation
  • Renal stones
  • An unintentional, oscillating to-and-fro muscle movement about a joint axis (tremor)
  • Muscles contract and relax quickly and cause uncontrolled shaking of the body (convulsion)

How is it diagnosed?

Cystathioninuria can be tested for by doing a blood or urine test and looking for elevated levels of Cystathionine in both. Biopsy may be necessary. DNA test can confirm the diagnosis.

It is currently not tested for in the newborn heel-prick tes

Can it be treated?

Cystathioninuria is a benign condition, it doesn’t cause many problems within the body. It can generally be treated with increased consumption of Vitamin B6 within the diet. A specialist dietician will explain how to increase Vitamin B6 within in your diet. Any dietary changes must be made under the supervision of your dietician.

Overall, you can live a happy and healthy lifestyle, whilst living with Cystathioninuria.

Do my family need to be tested?

Cystathioninuria is an autosomal recessive disease, meaning that a fault copy of the gene must be inherited from both parents, giving a 25% chance of the child being born with the disorder. There is a 50% chance that the child will be born carrier, which means that the child will only inherit one copy of the gene and cannot develop Cystathioninuria.  

As it is an autosomal recessive disorder, members of your family may be carriers, or they may have the deficiency and do not know. Genetic testing can be done for the disorder and can catch the disorder early on. Identifying carriers within your family can also assist in any family planning.

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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