Metabolic manipulation

Some inborn errors of metabolism due to enzyme deficiencies
can be treated effectively. Although direct replacement of the
missing enzyme is not generally possible, enzyme activity can
be enhanced in some disorders. For example, phenobarbitone
induces hepatic glucuronyl transferase activity and may lower
circulating concentrations of unconjugated bilirubin in the
Crigler–Najjar syndrome type 2. Vitamins act as cofactors in
certain enzymatic reactions and can be effective if given in doses
above the usual physiological requirements. For example,
homocystinuria may respond to treatment with vitamin B6,
certain types of methylmalonic aciduria to vitamin B12, and
multiple carboxylase deficiency to biotin. It may also be possible
to stimulate alternate metabolic pathways. For example,
thiamine may permit a switch to pyruvate metabolism by means
of pyruvate dehydrogenase in pyruvate carboxylase deficiency.