HYPERMETHIONINEMIA in infancy occurs regularly with homocystinuria due to cystathionine synthase deficiency.1,2 It has also been seen in association with hereditary tyrosinemia3 and with neonatal hepatitis.4 Interest in the early detection of hypermethioninemia has been stimulated by the fact that homocystinuria due to cystathionine synthase deficiency is one of the more common inborn errors of amino acid metabolism and by the possibility that brain damage in this condition may be prevented by a special low-methionine diet.1
In 1966 the Massachusetts Metabolic Screening Program conducted by the State Laboratory Institute, Massachusetts Department of Public Health, incorporated blood filter paper chromatography for the detection of hypermethioninemia and other hyperaminoacidemias in newborn and 4- to 10-week-old infants.5,6 In January 1968, the Guthrie bacterial inhibition assay for methionine (R. Guthrie, unpublished data) was included as a standard test for all blood specimens received in the Massachusetts screening program. These