Vitamin B Deficiencies

B1 — Thiamine Deficiency

• Syndromes: Beriberi and Wernicke-Korsakoff syndrome
• Dry beriberi: Peripheral neuropathy (sensory, motor, and reflex loss)
• Wet beriberi: High-output cardiac failure, edema, cardiomegaly
• Wernicke's encephalopathy: Confusion, ophthalmoplegia, ataxia (classic triad)
• Korsakoff's psychosis: Anterograde amnesia, confabulation (chronic/irreversible stage)
• At-risk groups: Alcoholics, malnutrition, prolonged IV feeding without supplementation

B2 — Riboflavin Deficiency

• Manifestations: Primarily mucocutaneous lesions
  • Angular stomatitis (cracks at corners of the mouth)
  • Glossitis (magenta/inflamed tongue)
  • Seborrheic dermatitis (especially nasolabial folds)
  • Corneal vascularization (neovascularization of the cornea)
  • Normochromic normocytic anemia
  • Personality changes
• Symptoms often overlap with other B-vitamin deficiencies (Harrison's, p. 9225)

B3 — Niacin Deficiency

• Syndrome: Pellagra — the "3 (or 4) Ds":
  1. Dermatitis — photosensitive skin rash (Casal's necklace on the neck)
  2. Diarrhea — GI inflammation, watery or bloody stools
  3. Dementia — cognitive decline, confusion, psychosis
  4. Death — if untreated
• Also seen in carcinoid syndrome (tryptophan diverted away from niacin synthesis) and Hartnup disease

B5 — Pantothenic Acid Deficiency

• Very rare in isolation (found in nearly all foods)
• Manifestations: Burning feet syndrome, fatigue, headache, insomnia, GI disturbances, numbness/tingling in extremities
• Usually only seen in severe malnutrition or experimental deficiency states

B6 — Pyridoxine Deficiency

• Manifestations:
  • Peripheral neuropathy
  • Seborrheic dermatitis
  • Glossitis and angular stomatitis
  • Microcytic sideroblastic anemia (impaired heme synthesis)
  • Irritability, confusion, depression
  • Seizures (especially in infants — critical for neonatal seizure workup)
  • Elevated homocysteine
• Also caused iatrogenically by isoniazid (INH) therapy — B6 supplementation is co-administered

B7 — Biotin Deficiency

• Rare; seen with raw egg white consumption (avidin binds biotin), or prolonged parenteral nutrition
• Manifestations:
  • Alopecia (hair loss)
  • Scaly, erythematous periorificial dermatitis
  • Conjunctivitis
  • Neurological symptoms: lethargy, hypotonia, seizures, developmental delay (in children)
  • Lactic acidosis (impaired carboxylase enzymes)

B9 — Folate (Folic Acid) Deficiency

• Manifestations:
  • Megaloblastic macrocytic anemia — identical blood picture to B12 deficiency
  • Glossitis, diarrhea
  • Neural tube defects (spina bifida, anencephaly) in the fetus — critical in pregnancy
  • Elevated homocysteine
• Key distinction from B12 deficiency: Folate deficiency does not cause subacute combined degeneration of the spinal cord (no neurological signs)
• At-risk: pregnancy, alcoholism, malabsorption (celiac disease), methotrexate use

B12 — Cobalamin Deficiency

• Manifestations:
  • Megaloblastic macrocytic anemia with hypersegmented neutrophils
  • Subacute combined degeneration of the spinal cord — demyelination of the dorsal and lateral columns → loss of vibration/proprioception, spastic weakness
  • Glossitis (beefy red tongue)
  • Psychiatric symptoms: depression, psychosis ("megaloblastic madness")
  • Elevated homocysteine and methylmalonic acid (MMA) — MMA is the distinguishing marker from folate deficiency
• Causes: Pernicious anemia (anti-intrinsic factor antibodies), strict veganism, gastric bypass, ileal disease/resection, chronic metformin use

Quick Summary Table