Delta 4-3-Oxysterol 5-Beta-Reductase Deficiency

What else is it called?

  • Congenital bile acid synthesis defect type 2
  • BASD2
  • Cholestasis with delta (4)-3-oxosteroid 5-beta-reductase deficiency
  • CBAS2

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What causes it?

This disorder is caused by a mutation in the AKR1D1 gene. This gene provides instructions for making a 3-oxo-5- beta(β)-steroid 4-dehydrogenase enzyme which is responsible for the production of bile acid in some liver cells. These acids are made from cholesterol and are found in your liver. They are needed to:

• Help make sure bile flows around your body

• Excrete bile from your body

• Help your intestines absorb fat and fat-soluble vitamins

• Break down and get rid of cholesterol from your body

If there is a problem making bile acids properly they will build up in your body along with cholesterol and other substances. These then become toxic and cause damage to your organs.

Specifically, if you have a problem in this gene, you will not produce enough of the 3-oxo-5- beta(β)-steroid 4-dehydrogenase enzyme. Therefore, subsequent chemical reactions requiring normal delivery of this enzyme will be impaired. Abnormal bile acid compounds will be produced instead which will prevent their transport out of the liver into the intestine, where the bile acids are needed to absorb fats and fat-soluble vitamins such as vitamins A, D, E, and K. As a result, you will not absorb fat-soluble vitamins and abnormal bile acids will build up in the liver alongside with cholesterol.

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. It is also unknown, whether it affects more men or women or any specific ethnic group. It is estimated, that generally congenital defects of bile acid synthesis are diagnosed in 1 to 9 individuals out of 1 million people.

What are the signs and symptoms?

The signs and symptoms may start to appear after birth or during infancy and they may include:

• Failure to gain weight and grow at the expected rate (failure to thrive)

• Yellowing of the skin and eyes (jaundice)

• Excess fat in the feces (steatorrhea)

• liver abnormalities including inflammation or chronic liver disease (cirrhosis)

• Enlarged liver (hepatomegaly)

• Softening and weakening of the bones (rickets)

• Problems with blood clotting that lead to prolonged bleeding

Early detection and treatment are important to prevent cirrhosis and death in childhood. Consequently, the early treatment promises an excellent long-term prognosis.

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 urine by performing specialized tests called secondary ionization mass spectrometry (LSIMS) and gas chromatography-mass spectrometry (GC-MS). A specialised diagnostic procedure called liver biopsy may be also performed. A genetic test can confirm the diagnosis.

Can it be treated?

Treatment of this disorder 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. It may involve a support from paediatrician and liver specialist.

Specifically, the treatment is based on bile acid replacement therapy and vitamin supplementation. Ursodeoxycholic acid (UDCA) therapy may also be considered. If no improvement is reached through other treatment methods, liver transplantation might be required

Do my family need to be tested?

Delta 4-3-Oxysterol 5-Beta-Reductase 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 Delta 4-3-Oxysterol 5-Beta-Reductase 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 Helen Morris by phoning 0845 241 2173 or emailing [Resource Library No: AAP002].

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