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An inborn error of ketone body catabolism resulting in intermittent episodes of ketoacidosis.

SCOT Deficiency; Succinyl-CoA:3-Oxoacid-CoA Transferase Deficiency; Succinyl-CoA: Ketoacid-CoA Transferase Deficiency; Succinyl-CoA:Acetoacetate Transferase Deficiency.

Less than 25 cases have been reported in the literature.

Autosomal recessive. Gene map location is chromosome 5p12-p13. Prenatal diagnosis can be made because cultured amniocytes have measurable succinyl-CoA:3-ketoacid CoA transferase (SCOT) activity.

SCOT, the key enzyme of ketone body utilization, is an extrahepatic mitochondrial matrix enzyme necessary for synthesis of acetoacetyl-CoA by transfer of a CoA moiety from succinyl-CoA to acetoacetate. Ketoacidosis is caused by SCOT deficiency resulting in reduced ketone body utilization.

Laboratory findings include succinyl-CoA:3-ketoacid-CoA transferase deficiency, together with ketonuria. Normal levels of plasma amino acids, lactic acid, ammonia, glucose, and organic acids other than beta-hydroxybutyrate and acetoacetate.

Severe intermittent ketoacidosis in ketogenic situations (fasting, febrile illness, any cause of stress) with no symptoms between episodes. There is persistent ketonuria, even in postprandial times. Age of onset is variable; however, a neonatal onset is common. The main clinical symptoms are vomiting and tachypnea.

Need to exclude diabetes mellitus and type I glycogen storage disease. Ensure adequate fluid resuscitation and treatment. Treatment consists of limiting protein intake, providing adequate calorie intake, and preventing aggravation of ketosis by providing alkaline therapy at the onset of any intercurrent infection. Check blood glucose, electrolyte levels, and blood gases with acid-base status.

Risk of pulmonary aspiration during induction of anesthesia is increased. Maintain adequate hydration. Close monitoring of blood gases in the perioperative period is required.

No known specific pharmacological implications with this condition. Infections may exacerbate ketoacidosis further. The threshold to use antibiotics should therefore be low.

Other constitutional causes of ketosis in children (differential diagnosis is made by enzyme assay), namely the following:

Ketotic Hypoglycemia: Unclear disorder associating ketosis and hypoglycemia; there is a carbohydrate deprivation with dependence on adipose tissue as sources of energy.

Mitochondrial Acetoacetyl-CoA Thiolase (ACAT) Deficiency: Autosomal recessive disorder of isoleucine and ketone body metabolism characterized by recurrent episodes of metabolic acidosis, hypoglycemia, lethargy, and coma as a consequence of the defective mitochondrial enzyme acetoacetyl-CoA thiolase that allows conversion of fat to energy (especially in fasted patients).

Snyderman SE, Sansaricq C, Middleton B: Succinyl CoA:3-ketoacid CoA transferase deficiency. Pediatrics 101:709, 1998.  [PubMed: 9521962]

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