Abstract
Plasma folate levels were measured in 3 homocystinurics and found to be <1 ng/ml (normal 5–10 ng/ml). All were on unrestricted, constant protein diets while 2 (A and B) were taking anticonvulsants for seizure control. Patient A had anemia (8.0 G% hemoglobin) and macrocytosis that responded to folic acid. B had macrocytosis but no anemia while C had neither. Plasma folate levels ranged from 14–20 ng/ml after therapy. Within 3 months of discontinuing folic acid in B and C their blood folates had fallen to 2.0 and 2.6 ng/ml. Plasma B12 levels and excretion of methyl-malonate were normal.
Plasma and urine amino acids responded to folic acid as noted in the table:
Methylation of homocystine to methionine requires folic acid. Many homocystinurics may increase methylation to methionine thereby requiring more folate and increasing glycine as a result of demethylation of serine. Some homocystinurics may require long-term folic acid supplementation (A and B) whereas others are unresponsive either biochemically or hematologically (C). (Supported in part by USPHS grants AM-02231 and HD-04837.)
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Morrow, G., Meltzer, D. & Barness, L. Effect of Folic Acid on Amino Acid Metabolism in Pyridoxine Unresponsive Homocystinurics. Pediatr Res 4, 453 (1970). https://doi.org/10.1203/00006450-197009000-00078
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DOI: https://doi.org/10.1203/00006450-197009000-00078
