LCHADD is an inherited fatty acid oxidation disorder caused by deficiency or ineffective functioning of an enzyme called “long-chain 3-hydroxyacyl-CoA dehydrogenase” (LCHAD). Without this enzyme, certain fats called “long-chain fatty acids” cannot be broken down properly.
Fatty acids are a major source of energy for the heart and muscles. During periods of fasting, fatty acids are also an important energy source for the liver and other tissues. When long-chain fatty acids are not metabolized properly, they cannot be converted to energy resulting in low blood sugar level (hypoglycaemia) and lethargy. At the same time, other toxic metabolites may also build up inside cells and damage multiple organs including the liver, heart and muscles.
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Our body breaks down fats from food into fatty acids when we eat, and breaks down fats from the body stores into fatty acids during prolonged fasting and stress for energy production. Long-chain 3-hydroxyacyl-CoA dehydrogenase is an enzyme that converts specific types of fatty acids namely long-chain fatty acids into energy. In people with LCHADD, the long-chain 3-hydroxyacyl-CoA dehydrogenase is either missing or function improperly. As a result, energy production is disrupted and metabolites build up in the body to harmful levels, causing serious health problems.
Everybody has two copies of genes, one from each parent, which tell the body how to make specific enzymes.
Long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency is an autosomal recessive disease. Only when babies inherit two faulty copies of the gene for long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency from parents, the enzyme made does not work properly or is not even made at all.
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Autosomal recessive inheritance
In autosomal recessive diseases, people with two faulty copies of gene (one from father and one from mother) will develop symptoms. People with only one faulty copy of gene will be normal that they are called disease carriers. LCHADD is inherited in autosomal recessive manner.
If both parents are LCHADD carriers, for each pregnancy (no matter it is a baby boy or girl), there is a 25% (1 in 4) chance that the child has 2 copies of normal gene (whom is not affected), 50% (1 in 2) chance that the child has with one normal and one faulty gene whom is a carrier just like parents, and 25% (1 in 4) chance that the child has two copies of faulty gene that at risk for LCHADD.
LCHADD can be very variable causing intermediate effects in some patients and more serious problems in others. Symptoms may start in the neonatal period or later in life.
However, if LCHADD is not diagnosed early, some patients may develop problems in early infancy or childhood with episodic bouts of illness called metabolic crisis.
Metabolic paediatricians and dieticians will work together to give expert advice and care to the babies with LCHADD. When necessary, treatment is usually needed throughout the life. The goal of treatment is to prevent metabolic crisis and accumulation of toxic metabolites.
It is important that babies with LCHADD be fed regularly and do not go for long periods without eating.
It is also very important is to discuss and design a care plan with your doctor and dietician beforehand, to let you know how to care for and provide extra sugary foods during illness or when your baby is not feeding well to prevent a metabolic crisis.
If you are worried that your baby is ill, it is important to follow medical advice. Bring your baby to your local accident and emergency department immediately. Take any information that you have been given about LCHADD, including this pamphlet, to the hospital with you.
For general queries on Newborn Screening Programme for Inborn Errors of Metabolism, please call 5741 4280 (Department of Clinical Genetics, Hospital Authority)
March 2026
Hospital Authority