Thiamine (B1) deficiency

Thiamine

• Biochemistry
• Metabolically active form: Thiamine pyrophosphate
• Enzyme systems
• a-ketoglutarate dehydrogenase: Krebs cycle
• Pyruvate dehydrogenase: Pyruvate Æ Acetyl CoA
• Transketolase: Pentose monophosphate shunt
• Sources: Yeast, Pork, Legumes, Cereal grains, Rice
• Clinical features
• Extraocular movement paresis
• Peripheral neuropathy
• Distribution: Symmetric
• Weakness: Distal; Legs (Foot dorsiflexors) & Hands (Wrist extensors)
• Pain: Burning feet; Lancinating pain; Calf tenderness
• Sensory loss
• Autonomic neuropathy: Orthostatic hypotension
• Tendon reflexes: Reduced in Legs
• Cranial nerve weakness (Occasional): Laryngeal (Hoarseness), Face & Tongue
• Cerebellar degeneration
• Encephalopathy
• Acute: Wernicke's disease
• Mental status D: Confusion; Memory loss; Agitation
• Ataxia: Especially truncal
• Ocular: Paresis; Nystagmus; Retinal hemorrhages
• Chronic: Korsakoff's psychosis
• Memory disorders
• Dementia
• Systemic
• Cardiac failure: Congestive; Tachycardia; Edema
• Infantile: Acute cardiac failure
• Associated or causative disorders
• Alcoholism
• Malnutrition: Polished rice; HIV infection; Systemic malignancy; Anorexia nervosa
• Dialysis
• Malabsorption & repeated vomiting: Gastric resection; Pregnancy
• Diet with thiaminases: Raw fish (carp)
• Diagnosis
• Transketolase activity: Whole blood or Erythrocyte
• Increased RBC Transketolase activity after addition of thiamine diphosphate (TPP)
• Urine thiamine excretion: 24 hour
• Other lab: High Serum pyruvate
• Pathology: Axonal degeneration
• Treatment
• Thiamine
• Acute
• Immediate: 100 mg/ml solution; Give 100 mg iv before glucose
• Follow-up: 100 mg i.m. for 3 to 5 days
• Chronic therapy: 50 mg i.m. for 2 weeks, then, Thiamine 50 mg p.o. per day
• Prophylactic: Treat with thiamine before giving i.v. glucose
• Response: Oculomotor D best; Dementia & Neuropathy less well