The C677T mutation in the methylenetetrahydrofolate reductase gene predisposes to hyperhomocysteinemia in children with familial hypercholesterolemia treated with cholestyramine.

In children with familial hypercholesterolemia, heterozygosity and homozygosity for the C677T mutation in the methylenetetrahydrofolate reductase gene was associated with low serum folate and increased susceptibility to elevation of plasma total homocysteine during cholestyramine treatment. Because of the independent relationship between elevated plasma total homocysteine and cardiovascular disease, folate supplementation may be prudent in these children.