ACYL-COA DEHYDROGENASE, MEDIUM CHAIN, DEFICIENCY OF: WHAT IS ACYL-COA DEHYDROGENASE, MEDIUM CHAIN, DEFICIENCY OF?
Definition: What is "Acyl-CoA dehydrogenase, medium chain, deficiency of"?
Acyl-coa dehydrogenase, medium chain, deficiency of definition: Medium Chain Acyl-CoA Dehydrogenase Deficiency (MCADD) is a rare hereditary disease that is the result of the lack of an enzyme required to convert fat to energy. People with MCADD cannot refrain from eating for very long. Fasting starts after the body has used all the food that the person has eaten, then begins to use the body's own fat to make energy. When people with MCADD fast, they can experience a variety of serious life threatening symptoms or even death. Persons with MCADD cannot utilize this fat to make energy, consequently, the body begins to fail & malfunction once the food the person has eaten runs out.
Symptoms & Signs
Some individuals affected by MCADD have recurrent episodes of lethargy, metabolic acidosis, hypoglycemia & coma. Symptoms usually begin early on in infancy or childhood. Some affected individuals, however, have no apparent symptoms at birth, but low blood sugar, seizures, brain damage, cardiac arrest & serious illness can occur very quickly in children who are not feeding well. As much as a quarter of affected individuals die in their first crisis so it is imperative to know that a person has this disease so that crisis can be prevented. More than half of individuals with MCADD die from their first crisis if it occurs after the age of two. MCADD occurs chiefly among Caucasians of northern European background.
The gene that causes this condition has been mapped to locus 1p31; several allelic variations have been reported. The most frequent mutation is 985A>G, which refers to a substitution of a guanine nucleotide for an adenine nucleotide at the 985th residue. A second mutation, 583G>A, is reportedly common in specific populations. One study reported that individuals homozygous for 985A>G or 583G>A mutations had the greatest levels of octanoylcarnitine, even when asymptomatic & had the most severe clinical manifestations. Phenotype-genotype relationships have been sought, with little or no success. As an example, although the common 985A>G mutation is commonly responsible for infantile onset, the same mutation has been reported in a patient with adult onset. Acute hepatic failure in a previously healthy gravid female who is homozygous for the 985A>G mutation has been reported, hence confirming the potential for later onset, as well as the severity of complications with this specific mutation.
The application of tandem mass spectrometry to newborn metabolic screening in many other countries throughout the world has provided a better understanding of the worldwide incidence of MCAD deficiency. The mean incidence rate among more than 8 million babies was 1 per 14,600 live births, with a range of 1 per 13,500 to 1 per 15,900. A single mutation accounted for more than half of all diagnosed cases.