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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. 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. 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. ==Signs and symptoms== MCADD presents in early childhood with hypoketotic hypoglycemia and liver dysfunction, often preceded by extended periods of fasting or an infection with vomiting. Infants who are exclusively breast-fed may present in this manner shortly after birth, due to poor feeding. In some individuals the first manifestation of MCADD may be sudden death following a minor illness. A number of individuals with MCADD may remain completely asymptomatic, provided they never encounter a situation that sufficiently stresses their metabolism.〔〔 With the advent of expanded newborn screening, some mothers have been identified with MCADD after their infants had positive newborn screens for low carnitine levels. The enzyme ''MCAD'' is responsible for the dehydrogenation step of fatty acids with chain lengths between 6 and 12 carbons as they undergo beta-oxidation in the mitochondria. Fatty acid beta-oxidation provides energy after the body has used up its stores of glucose and glycogen. This oxidation typically occurs during periods of extended fasting or illness when caloric intake is reduced, and energy needs are increased. Beta-oxidation of long chain fatty acids produces two carbon units, acetyl-CoA and the reducing equivalents NADH and FADH2. NADH and FADH2 enter the electron transport chain and are used to make ATP. Acetyl-CoA enters the Krebs Cycle and is also used to make ATP via the electron transport chain and substrate level phosphorylation. When the supply of acetyl-CoA (coming from the beta-oxidation of fatty acids) exceeds the capacity of the Krebs Cycle to metabolize acetyl-CoA, the excess acetyl-CoA molecules are converted to ketone bodies (acetoacetate and beta-hydroxybutyrate) by HMG-CoA synthase in the liver. Ketone bodies can also be used for energy especially by the brain and heart; in fact they become the main sources of energy for those two organs after day three of starvation. 〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Medium-chain acyl-coenzyme A dehydrogenase deficiency」の詳細全文を読む スポンサード リンク
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