Population Screening

To the Editor: In their review article, Khoury et al. (Jan. 2 issue) 1 suggest that homocystinuria should be screened for by Guthrie bacterial inhibition assay and treated with vitamin B 12 and methionine restriction. Homocystinuria occurs in several conditions, including cystathionine β-synthase deficiency and genetic disorders of homocysteine remethylation. 2 , 3 Plasma total homocysteine levels may also be elevated because of folate deficiency or vitamin B 12 deficiency. 2 The Guthrie test, designed to detect hypermethioninemia, fails to detect abnormalities of homocysteine remethylation. Hypermethioninemia occurs not only in cystathionine β-synthase deficiency but also in a variety of other conditions. 2 , 4 , 5 Cystathionine . . .