MTR and Decreased methionine synthase activity: A 2014 case-report [53] on three patients with remethylation defects (one with methionine synthase deficiency (cblG) and two with methyltetrahydrofolate reductase deficiency (MTHFR), all intubated for respiratory failure, described clinical improvement thanks to medical treatment with betaine and folinic acid supplementation in all three, methionine in two, and cobalamin supplementation in two.