Inherited metabolic disorder resulting in ketoacidotic episodes.
Succinyl-CoA:3-Oxoacid CoA-Transferase (SCOT) Deficiency.
Extremely rare disorder (fewer than 30 patients described).
Autosomal recessive transmission.
Mutations in OXCT1 gene on 5p13. SCOT is an extrahepatic, mitochondrial matrix protein necessary for the synthesis of acetoacetyl-CoA from succinyl-CoA and acetoacetate. Acetoacetyl-CoA is then cleaved by mitochondrial acetyl-CoA thiolase and enters the tricarboxylic acid cycle. Of three different acetyl-CoA thiolases (a peroxisomal, a cytoplasmic, and a mitochondrial form), only the mitochondrial one needs to be considered here.
The disorder usually manifests as a severe ketoacidosis in the first week of life with tachypnea (caused by severe metabolic acidosis) being the most prominent sign (later onset has been described). Usually pyruvate, lactate, ammonia, and blood glucose levels are normal during the ketoacidotic event; however, hypoglycemia does not rule out succinyl-CoA:3-ketoacid CoA transferase (SCOT) deficiency. Similar to acylcoenzyme A cholesterol acyltransferase (ACAT) deficiency, the treatment of the ketoacidotic attacks consists of dextrose-containing fluid replacement therapy (keep blood glucose in the high normal range to suppress ketogenesis) and sodium bicarbonate. Common triggers of an attack are usually fever and/or infections, and the attacks tend to present more often with lethargy and coma after the neonatal period. Between these episodes the patients are free of symptoms, although elevated concentrations of ketone bodies in the urine can also be found during that time. Mildly restricted protein and fat intake should help to control ketogenesis. Some patients are on a carbohydrate-rich diet with oral sodium bicarbonate supplements.
Cardiomegaly and congestive heart failure have been described in some of these patients. The maintenance of high glucose level is mandatory to prevent ketoacidosis. Epidural analgesia has been described to minimize physiological stress.
Other condition to be considered
et al: Succinyl CoA:3-oxoacid CoA transferase (SCOT): Human cDNA cloning, human chromosomal mapping to 5p13, and mutation detection in a SCOT deficient patient. Am J Hum Genet
R: Management and communication problems in a patient with succinyl-CoA transferase deficiency in pregnancy and labour. Int J Obstet Anesth
et al: A structural mapping of mutations causing succinyl-CoA:3-ketoacid CoA transferase (SCOT) deficiency. J Inherit Metab Dis