Propionic acidemia (PPA). Propionyl-CoA carboxylase deficiency. Also called Ketotic Hyperglycinemia.
Incidence
10 to 15% of all organic acidurias. It is AR disease. All 5 enzymes of the urea cycle are depressed, with resultant hyperammonemia, confusing at times with urea cycle disorders.
Clinical Characteristics
Characterized by intermittent persistent vomiting, lethargy and ketolactic acidosis. Rarely biotin dependent. Early neonatal devastating metab. disease with ketolactic acidotic coma. Recurs with protein ingestion and infections.. Need massive amounts of alkali & glucose to control. Episodic low WBC. Devastating thrombocytopenia usually kill patients if unrecognized. In propionic acidemia severe lactic acidosis has been described. The latter may results from an inadequate supply of and an increased need for thiamine.
Precipitants
Ingestion of proteins and various aminoacids, notably isoleucine, valine, methionine,threonine. Infections. Continuos vomiting. Fasting will precipitate an attack due to movilization of fat.
Provocation Tests
Provocation tests are not recommended. Tandem MS are always diagnostic. L-Carnitine loading (100 mg/kg) leads to increased excretion of propionylcarnitine, hippurate and 4-hydroxyhippurate.
Diagnostic Procedures
(propionic acidemia): EB-F, EB-W, EB-liver, OB-F, Also see Holocarboxylase deficiency. DB or CB also. Tandem MS are always diagnostic. L-Carnitine loading (100 mg/kg) leads to increased excretion of propionylcarnitine, hippurate and 4-hydroxyhippurate.