Review Question - QID 106505

This newborn has elevated levels of hydroxypropionic acid and symptoms suggestive of propionic acidemia. Propionyl-CoA carboxylase is deficient in this patient.

Propionic acidemia is an autosomal recessive disorder caused by a deficiency of propionyl-CoA carboxylase in the propionic acid cycle. This deficiency results in the inability to metabolize VOMIT via the propionic acid cycle:

-Valine
-Odd-chain fatty acids (proprionic acid)
-Methionine
-Isoleucine
-Threonine

Patients present with ketoacidosis and have elevated blood levels of propionic acid, methyl citrate, and hydroxypropionic acid. Other defects of propionic acidemia include methylmalonyl-CoA mutase deficiency which results in elevated methylmalonic acid levels.

Incorrect Answers:
Answer 1: A deficiency in branched-chain ketoacid dehydrogenase results in maple syrup disease which has symptoms of lethargy, weight loss, hypotonia, mental retardation, and the classic sign of sweet smelling urine.
Answer 2: A deficiency in phenylalanine hydroxylase results in phenylketonuria which has symptoms of mental retardation, microcephaly, and a musty/mousy odor to the sweat and urine.
Answer 4: A deficiency in cystathionine synthase results in homocystinuria which results in vessel damage (DVT, atherosclerosis, and myocardial infarctions) and a presentation similar to Marfan's syndrome (mental retardation, lens dislocation, and a tall stature with long extremities).
Answer 5: A deficiency in homogentisate oxidase results in alkaptonuria which has symptoms of arthritis, darkening urine upon leaving in air, and discoloration of the skin and sclera.