Medium Chain 3-Ketoacyl-CoA Thiolase Deficiency

What else is it called?

  • MCKAT Deficiency 
  • MCKAT 
  • MCAT 

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What causes it?

Medium Chain 3-Ketoacyl-CoA Thiolase Deficiency is an extremely rare disorder caused by a problem in the genes. This gene produces an enzyme that helps to break down certain fats. 

If your child has a problem in this gene, they will not produce enough of the enzyme they need. This means they will be unable to break down important fats from their food that produce energy. Instead, these fats partially break down, releasing chemicals into the body that are toxic in large quantities. 

Very little is currently known about this disorder due to its rarity. 

How common is it?

Medium Chain 3-Ketoacyl-CoA Thiolase Deficiency is extremely rare and only one case has ever been reported and diagnosed. The case was a newborn baby from Japan in 1989. 


What are the signs and symptoms?

In the reported case, symptoms presented in the second day of life. These included: 

  • Vomiting/diarrhoea 
  • Dehydration 
  • Weight loss and poor appetite 
  • Difficulty breathing 
  • Acidic blood (metabolic acidosis) 
  • Liver dysfunction 
  • Breakdown of muscles (rhabdomyolysis) 
  • Red or brown coloured urine (myoglobinuria)  

The life expectancy of somebody with this disorder is difficult to assess because not many people have been diagnosed. In the case that has been reported, the baby lived until 13 days of age. 

How is it diagnosed?

Medium Chain 3-Ketoacyl-CoA Thiolase Deficiency is diagnosed using a specialised urine and blood test. A genetic test may also be required. 

This disorder comes under the category of fatty acid oxidation conditions. These conditions are all linked to the breakdown and use of fats in the body. Your child could be initially diagnosed with a similar fatty acid oxidation condition before being diagnosed with Medium Chain 3-Ketoacyl-CoA Thiolase Deficiency.  

Medium Chain 3-Ketoacyl-CoA Thiolase Deficiency is not currently on the list of disorders checked during the newborn screening process in the UK, but it is sometimes screened for in the USA. 

Can it be treated?

Treatment for Medium Chain 3-Ketoacyl-CoA Thiolase Deficiency only focuses on reducing the symptoms and supporting your child. This can include treatments like IV fluids and nutrition, which will usually be carried out in a hospital environment. Your medical team may also offer supplements, which is common in other fatty acid oxidation conditions. 

There are currently no treatments for the disorder itself. 

It is difficult to assess the long-term effects of Medium Chain 3-Ketoacyl-CoA Thiolase Deficiency because of its rarity. The only person to be diagnosed with this disorder died at 13 days old. 

Do my family need to be tested?

There is currently no information on how Medium Chain 3-Ketoacyl-CoA Thiolase Deficiency is inherited or developed.  

If your child has been diagnosed with this disorder, consult your medical team for guidance on further testing for family. 

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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