Vitamin B9 deficiency

Background
  • Also known as folate, folic acid
  • Necessary for normal erythropoiesis, purine and thymidylate synthesis, amino acids metabolism, and histidine metabolism
  • Found in most fruits and vegetables
  • Recommended daily intake: 400 mcg or 500-600mcg if pregnant or lactating
  • Total body stores of folate enough to supply requirements for 2–3 mo

Causes
  • Most common cause of deficiency is inadequate dietary intake, usually secondary to:
  • Other causes:
    • Decreased absorption
      • Tropical sprue
      • Drugs (phenytoin, sulfasalazine, trimethoprim-sulfamethoxazole
    • Increased requirement
    • Folate loss due to hemodialysis
    • Inhibition of reduction to active form (tetrahydrofolic acid) by methotrexate

Clinical Features
  • Signs/symptoms of anemia which may be severe
  • Glossitis
  • Vague GI disturbances (e.g. anorexia, diarrhea)
  • No neurologic features (unlike B12 deficiency)

Differential Diagnosis

Anemia

RBC Loss
  • Hemorrhage

RBC consumption (Destruction/hemolytic)

Impaired Production (Hypochromic/microcytic)
  • Iron deficiency
  • Anemia of chronic disease
  • Thalassemia
  • Sideroblastic anemia

Aplastic/myelodysplastic (normocytic)
  • Marrow failure
  • Chemicals (e.g. ETOH)
  • Radiation
  • Infection (HIV, parvo)

Megaloblastic (macrocytic)

Evaluation
  • CBC
    • Macrocytic anemia (MCV>100 fL)
    • RDW high
    • Hypersegmented neutrophils
  • Red blood cell folate level < 150 ng/mL

Management
  • Folate: up to 1mg IV/IM or PO daily
    • Maintenance: 0.4mg/day PO (non-pregnant/lactating) or 0.8mg/day PO (pregnant or lactating)

Disposition

See Also

References
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