II. Folate deficiency
A. Nutritional causes
1. Decreased dietary intakepoverty and famine, institutionalization (psychiatric facilities, nursing homes), chronic debilitating disease, prolonged feeding of infants
with goats milk, special slimming diets or fad foods (folate-rich foods not consumed), cultural or ethnic cooking techniques (food folate destroyed)
2. Decreased dietary intake and increased requirements
a. Physiologicpregnancy and lactation, prematurity, hyperemesis gravidarum, infancy
b. Pathologic
(1) Intrinsic hematologic diseases involving hemolysis with compensatory erythropoiesis, abnormal hematopoiesis, or bone marrow infiltration by malignant
disease
(2) Dermatologic diseasepsoriasis
B. Folate malabsorption
1. With normal intestinal mucosa
a. Drugssulfasalazine, pyrimethamine, proton pump inhibitors (via inhibition of proton-coupled folate transporters)
b. Hereditary folate malabsorption (mutations in proton-coupled folate transporters) (rare)
2. With mucosal abnormalitiestropical/nontropical sprue, regional enteritis
C. Defective CSF folate transportcerebral folate deficiency (autoantibodies to folate receptors) (rare)
D. Inadequate cellular utilization
1. Folate antagonists (methotrexate)
2. Hereditary enzyme deficiencies involving folate
E. Drugs (multiple effects on folate metabolism)alcohol, sulfasalazine, triamterene, pyrimethamine, trimethoprim-sulfamethoxazole, phenytoin, barbiturates