A rare disorder where a mother suffering from phenylketonuria during pregnancy can result in various birth abnormalities.
* Mental deficiency * Low I.Q. * Increased muscle tone * Pigeon-toed gait * Growth deficiency
PKU is transmitted by an autosomal recessive gene on chromosome 12. Patients with this disorder have insufficient hepatic phenylalanine hydroxylase, an enzyme that acts as a catalyst in the conversion of phenylalanine to tyrosine. As a result, phenylalanine and its metabolites accumulate in the blood, eventually causing mental retardation if left untreated. The exact biochemical mechanism that causes this retardation is unclear.
Treatment consists of restricting dietary intake of the amino acid phenylalanine to keep phenylalanine blood levels between 3 and 9 mg/dl. Because most natural proteins contain 5% phenylalanine, they must be limited in the child's diet. An enzymatic hydrolysate of casein, such as Lofenalac powder or Pregestimil powder, is substituted for milk in the diets of affected infants. This milk substitute contains a minimal amount of phenylalanine, normal amounts of other amino acids, and added amounts of carbohydrate and fat. Dietary restrictions usually continue throughout life.