Background: Autosomal recessive inborn errors of metabolism often present as life-threatening disease in infancy and have adverse effects on the nervous system. Parents are usually heterozygotes. This is true of most disorders of fatty acid oxidation, which are rare and present with hypoketotic hypoglycemia. However, the gene for medium-chain acyl coenzyme A dehydrogenase (MCAD) deficiency is common in white people, raising the possibility that a parent may be homozygous.
Objective: To document the occurrence of MCAD deficiency in a 12-month-old boy and his father, both of whom were homozygous for the A985G mutation.
Design: Clinical observations and definitive biochemical testing.
Setting: Children's hospital and university laboratory.
Participants: One child and one adult.
Interventions: Diagnosis and treatment.
Main outcome measures: Clinical outcome; analysis results of plasma and urine for carnitine and organic acids.
Results: An infant admitted with an acute illness requiring intensive care was found to have carnitine deficiency and dicarboxylic aciduria; MCAD deficiency was diagnosed by assay of his DNA for the common mutation. Test results of the father revealed him also to be homozygous.
Conclusion: In MCAD deficiency, as opposed to the usual rare autosomal recessive metabolic disease, a parent may also be an affected homozygote.