Short-chain acyl-coenzyme A dehydrogenase deficiency

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Short-chain acyl-coenzyme A dehydrogenase deficiency (or "SCADD") is a fatty acid oxidation disorder which affects enzymes required to break down a certain group of fats called short-chain fatty acids.

Diagnosis

Some affected infants will exhibit vomiting, low blood sugar (hypoglycemia), a lack of energy (lethargy), poor feeding, and failure to gain weight and grow at the expected rate (failure to thrive). Other features of this disorder may include poor muscle tone (hypotonia), seizures, developmental delays, and a small head size (microcephaly). The symptoms of short-chain acyl-CoA dehydrogenase deficiency may be triggered by periods of fasting or during illnesses such as viral infections. In some cases, signs and symptoms may not appear until adulthood, when some individuals may develop muscle weakness and wasting. Other people with gene mutations that can cause this disorder may have such mild symptoms that they are never diagnosed. Many biochemical geneticists consider this to be a biochemical phenotype with a very mild clinical phenotype or no clinical phenotype.

Genetics

Mutations in the ACADS gene cause short-chain acyl-coenzyme A dehydrogenase deficiency. Mutations in the ACADS gene lead to inadequate levels of an enzyme called short-chain acyl-CoA dehydrogenase. This enzyme is important for the breakdown of short-chain fatty acids. Reduced levels of this enzyme prevent short-chain fatty acids from being further broken down and processed in the mitochondria (the energy-producing centers inside cells). As a result, these short-chain fatty acids are not converted into energy, which can lead to the signs and symptoms of this disorder, such as lethargy and hypoglycemia.

This condition is an autosomal recessive disorder, which means two copies of the faulty gene must be inherited to be afflicted with the disorder. Most often, the parents of an individual with an autosomal recessive disorder are carriers of one copy of the altered gene, but do not have the disorder. This disorder is thought to affect approximately 1 in 40,000 to 100,000 newborns.