Vitamin deficiencies

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  • i. Thiamine deficiency (B1)
    • 1. causes Wernicke’s encephalopathy and beri-beri
      • a. Wernicke’s encephalopathy usually complicates chronic alcoholism and is thought to be due to the energy deficit that results from impaired enzyme activity
      • b. Wernicke’s encephalopathy usually manifests acutely with gaze palsies, confusion, nystagmus and ataxia which respond rapidly to thiamine administration
      • c. Wernicke’s encephalopathy is sometimes associated with Korsakoff’s psychosis which is characterized by retrograde and anterograde amnesia that does not respond to thiamine and is usually irreversible (Wernicke’s + Korsakoff’s psychosis = Wernicke-Korsakoff syndrome)
      • d. Microscopically see necrosis in the mamillary body with sparing of neurons, capillary endothelial hyeprplasia and cuffing by macrophages, petechial hemorrhages, loss of myelinated fibers
    • 2. lesions usually in the mamillary bodies but may also involve the hypothalamus
      • ii. nicotinic acid (niacin, B3 or its precursor tryptophan) deficiency
        • 1. Betz cells and neurons in the pons and cerebellar dentate nuclei show striking chromatolysis
        • 2. pallagra
          • a. classic clinical triad of dermatitis, diarrhea, and dementia
          • b. may also include hyperpigmentation and ulceration of sun exposed skin, impaired memory, apathy, delirium, seizures, myelopathy with spastic weakness, and peripheral neuropathy
          • c. seen in pure vegetarians
          • d. Remember: Pure vegetarians and Hartnup patients suffer from the 3 D’s: diarrhea, dementia and dermatitis (think of 17th century sailors making long trips without good food)
        • 3. Hartnup disease – intestinal malabsorption of tryptophan and other neutral amino acids; treatment is with nicotinamide because excess tryptophan is not absorbed through the intestine
      • iii. pyridoxine (B6)
        • 1. can cause irritability and will lower seizure threshold
        • 2. impairs synthesis of niacin from tryptophan
        • 3. must be given to patients receiving isoniazid to prevent peripheral neuropathy
      • iv. pantothenic acid
        • 1. deficiency can cause paresthesias and “burning feet” along with lesions of peripheral nerves
      • v. folic acid
        • 1. symptoms resemble that of B12 deficiency (paresthesias, sensory impairment, and weakness predominantly in the lower limbs)
        • 2. associated with neural tube defects
      • vi. vitamin A deficiency
        • 1. associated with night blindness (nyctalopia) and rarely increased ICP in children
        • 2. vitamin A toxicity leads to brain and liver swelling
      • vii. vitamin E deficiency
        • 1. associated with cystic fibrosis
        • 2. may cause swelling and degeneration of the distal part of longer axons in peripheral nerves and posterior spinal, spinocerebellar and corticospinal tracts
        • 3. symptoms: peripheral neuropathy and spinocerebellar dysfunction that may resemble Friedreich’s ataxia; Remember: vitamin ‘E’ and FrEEdrich’s
      • viii. protein deficiency (kwashiorkor)
        • 1. CNS manifestations are late but may have irritability, little spontaneous movement or tremor
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