Folate deficiency is relatively common as a cause of macrocytic anemia. And, deficiencies during pregnancy are related to increased rates of congenital birth defects.

Clinical Signs of Possible Folate Deficiency Disease

• macrocytic anemia (megaloblastic bone marrow morphology) when pure deficiency
• normocytic when combined with iron deficiency

Causes of elevated serum folate levels:

• excessive vitamin or multivitamin intake
• other

Causes of decreased serum levels of folate:

• dietary deficiency of  folate
• pregnancy
• chronic liver disease (especially ethanol abuse)
• situations with rapid cell turnover causing a depleting hyperdemand for folate (such as compensating acute hemolytic anemia, leukemia/lymphoma, repair of huge cutaneous exfoliation or burn)
• non-classic celiac disease manifestation (20-50% of gluten sensitive patients); 1 in 250 whites, antibody serology
• malabsorption syndromes: celiac sprue
• chemotherapy and anticonvulsant medications

NOTES:

• LDH elevation: because the bone marrow erythropoiesis is "ineffective" and with intramedullary hemolysis in vitamin B12 or folate deficiency of any etiology, the serum LDH level is almost always elevated, but often much milder than with B12 deficiency. Iron deficiency exerts a hypoproliferative effect that retards the bulkiness of the B12 or folate deficient megaloblastic erythropoiesis, thereby retarding the quantity/rate of intramedullary hemolysis.
• folate deficient patients often have B12 levels at 100-200 ng/L (nl >200)
• pregnant patients often have B12 levels at 100-200 ng/L (nl >200)
• serum folate levels rapidly respond to intake from oral sources or transfusions
• RBC folate levels are a more accurate reflection of body stores of folate; but they are low in 60% of patients with clinical vitamin B12 deficiency (whereas the serum folate level is normal).

REFERENCES:

1. May 2001 LMC Lab internal memo