Isolated Defect of Folic Acid Absorption Associated with Mental Retardation and Cerebral Calcification

A 19 year old female is described with a clinical syndrome characterized by specific malabsorption of folate from the gut with resultant megaloblastic anemia associated with mental retardation and cerebral calcification. The absorption of fat, xylose, glucose, vitamin A and vitamin B₁₂ and the jejunal biopsy histology were all normal. The patient was unable to absorb folate in its naturally occurring form as pteroylpolyglutamic acid as well as pteroylmono-, pteroyldi-, pteroyltriglutamic acid, N⁵-formyltetrahydrofolic acid and N⁵-methyltetrahydrofolic acid. Folate absorption was not enhanced when pteroylmonoglutamic acid was premixed with normal human duodenal juice, lyophilized calf jejunum or lyophilized calf pancreas. Impairment of normal transport of folic acid from the blood into the cerebrospinal fluid was also demonstrated in this patient. Plasma folate clearance was normal and there was no increase in folate antagonists or in folate binding present in the patient’s plasma.