

Medium-chain acyl-coenzyme A dehydrogenase deficiency

From SNPedia

Medium-chain acyl-CoA dehydrogenase deficiency, often known as MCAD deficiency or MCADD, is a disorder of fatty acid oxidation that impairs the body's ability to break down medium-chain fatty acids into acetyl-CoA. The disorder is characterized by hypoglycemia and sudden death without timely intervention, most often brought on by periods of fasting or vomiting.Wikipedia

Prior to expanded newborn screening, MCADD was an underdiagnosed cause of sudden death in infants. Individuals who have been identified prior to the onset of symptoms have an excellent prognosis.Wikipedia

MCADD is most prevalent in individuals of Northern European Caucasian descent, with an incidence of 1:4000 to 1:17,000 depending on the population. Treatment of MCADD is mainly preventative, by avoiding fasting and other situations where the body relies on fatty acid oxidation to supply energy.Wikipedia

MCADD is inherited in an autosomal recessive manner, meaning an affected individual must inherit a mutated allele from both of their parents. ACADM is the gene involved, located at 1p31, with 12 exons and coding for a protein of 421 amino acids. There is a common mutation, rs77931234(C) (in dbSNP orientation), among Northern European Caucasians, which results in a lysine being replaced by a glutamic acid at position 304 of the protein (note: numbering may vary depending on reference). Other mutations have been identified more commonly since newborn screening has expanded the mutation spectrum. The 985A>G (rs77931234C) common mutation is present in the homozygous state in 80% of Caucasian individuals who presented clinically with MCADD and in 60% of the population identified by screening.Wikipedia

An individual's genotype does not correlate well with their clinical phenotype for MCADD. The clinical presentation of an individual with MCADD depends not only on the presence of the mutations in the ACADM gene, but also on the presence of environmental or physiological stressors that require the body to depend on fatty acid oxidation for energy. Some mutations, identified through newborn screening programs and associated with higher residual enzyme activity have not been seen in individuals with clinical symptoms of MCADD. Despite this, treatment with fasting avoidance remains the norm for all those diagnosed with MCADD.Wikipedia