... explain its reported association with a lower risk for colorectal cancer. Other Chapter 100. Megaloblastic Anemias (Part 5) An underlying maternal folate metabolic abnormality has also been ... severe homocystinuria (blood levels 100 µmol/L) due to deficiency of one of three enzymes, methionine synthase, MHTFR, or cystathionine synthase (Fig. 100- 1), suffer from vascular disease, ... has been identified: reduced activity of the enzyme 5,10-methylene-THF reductase (MTHFR) (Fig. 100- 1) caused by a common 677CÆT polymorphism in the MTHFR gene. In one study, the prevalence of...