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Défices vitamínicos

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Vitamin A Deficiency
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  • AKA Phrynoderma
  • Pathophysiology
    • Maintenance of epithelium - regulate transcription for growth, differentiation and maintenance of epithelial cells
    • Vision: epitélio pigmentado da retina contém retinal (sobretudo nos bastonetes)
    • Genes homebox: teratogénico porque interfere com estes genes
  • Clinical presentation
    • Multiple cluster of follicular papules
    • Follicular hyperkeratosis on extensor surfaces
    • Generalized xerosis
    • Sparse, fragile hair
    • Ocular abnormalities
      • Night blidness, xerophtalmia, Bitot’s spots (white spots on the conjunctiva), keratomalacia, blindness
    • Impaired intellect and apathy
    • Increased morbidity/mortality from infections (measles)
 
Vitamin K Deficiency
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  • Impairment in coagulation cascade
    • Gamma carboxylation of glutamate of prothrombin. O glutamato fica com 2 cargas negativas para conseguir atrair o Cálcio
  • Associated with
    • Fat malabsorption
    • Long-term antibiotic therapy
    • Breast-fed (no VitK in breast milk, GI is sterile in newbornsm no VitK in newborn liver - doesn’t cross placenta)
    • Infant whose mother was taking anticonvulsant therapy during pregnancy
  • Clinical presentation
    • Purpura, ecchymoses, hemorrhage
    • Prolonged prothrombin time
    • Subcutaneous injection can cause erythematous annular plaque
 
Vitamin C Deficiency (ascorbate)
  • Relevant biochemistry pathways
    • Anti-oxidant reaction
    • Prolyl and lysil hydroxylases (collagen synthesis)
    • Dopamine hydroxylase (catecholamine synthesis)
    • Absorption of iron in GI tract
  • Causes
    • Diet deficient in citrus fruits and green vegetables
  • Clinical presentation
    • Scurvy
      • Follicular hyperkeratosis (favors forearms, abdomen, legs) ~Vitamin A Deficiency
      • Corkscrew hairs with perifollicular hemorrhage
      • Petecchiae, ecchymoses, hemorrhage
      • Gingival hypertrophy with erosions
      • Poor wound healing
      • Hyperelastic skin
    • Microcytic anemia
    • Increased bleeding time (platelets cannot bind to defective collagen)
 
Vitamin B Deficiencies
  • Vitamin B1 - “Beriberi”
    • Relevant biochemistry pathways
      • Important for dehydrogenase reactions
        • Pyruvate dehydrogenase (responsible for lactic acidosis)
        • Alpha-ketoglutarate dehydrogenase (TCA cycle)
        • Transketolase (HMP shunt)
        • Branched chain ketoacid dehydrogenase
    • Causes
      • Alcoholism (alcohol interferes with absorption)
    • Clinical presentation
      • Wernicke - ataxia, nystagmus, ophtalmoplegia
      • Korsakoff (confabulation, psychosis)
      • Dry beri-beri - peripheral neuropathy
      • Wet beri-beri - high output cardiac failure, fluid retention, vascular leak
      • Edema, glossitis, glossodynia
  • Vitamin B2 - “Oro-oculo-genital syndrome” (riboflavin)
    • Painless scaly papules, ulcers, fissures, seborrheic changes in periorificial sites
    • “Severe Seborrheic Dermatitis” → similar to zinc deficiency
    • Atrophic glossitis, conjunctivitis, photophobia
  • Vitamin B3 - “Pellagra” (niacin)
    • No Saurat: “Vitamin PP comprises two substances: nicotinic acid (niacin) and nicotinamide
    • Relevant biochemistry pathways
      • Important in Ox/Red reactions
    • Causes
      • Also caused by deficiency in tryptophan (tryptophan→niacin)
    • Clinical presentation
      • Dermatitis, Diarrhea, Dementia, Death (4 D’s)
      • Photosensitive eruption - “Casal’s necklace”
      • Perianal inflammation and erosions
      • Edema, cheilitis, atrophic glossitis (corners of the mouth)
  • Vitamin B5 (pantothenic acid)
    • Alopecia with canities (canície) appears in animals during prolonged deficiencies
  • Vitamin B6 (pyridoxine)
    • Relevant biochemistry pathways
      • Transamination (movement of amino groups) reaction
        • Aminotransferase: AST, ALT (protein catabolism)
        • Aminolevulinate synthase (heme synthesis)
    • Causes
      • Drugs: isoniazid, penicillamine, hydralazine, OCP (also phenelzine and cycloserine, no longer used)
      • Alcoholism
    • Clinical presentation
      • Periorificial scaly eruption, conjunctivitis, stomatitis, glossitis
      • Sideroblastic anemia. (microcytic anemia)
      • Convulsions
    • Diagnosis
      • Tryptophan loading test (measurement of urinary xanthunuric acid)
  • Vitamin B12 (cyanocobalamine)
    • Relevant biochemistry pathways
      • Homocysteine methyltransferase
      • Methylmalonyl CoA mutase
    • Causes
      • Pernicious anemia
      • Aging
      • Poor nutrition
      • Bacterial overgrowth of terminal ileum
      • Resection of the terminal ileum secondary to Crohn disease
      • Chronic pancreatitis
      • Vegans
      • Infection with D. latum
    • Clinical presentation
      • Cutaneous
        • Generalized hyperpigmentation with flexural accentuation
        • Red, smooth, painful tongue
      • Megaloblastic anemia
      • Progressive peripheral neuropathy
    • Associations
      • Poliosis, vitiligo, alopecia areata
      • Associated with pernicious anemia
  • Folic acid (B9)
    • Relevant biochemistry pathways
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      • 1 carbon carrier (THF)
        • Thymidylate synthase (thymidine synthesis)
        • Enzymes in purine synthesis
      • Purine synthesis
    • Causes
      • Alcoholism and pregnancy
      • Body stores depleted in 3 months
      • Hemodialysis
    • Clinical presentation
      • Cheilitis, glossitis, mucosal erosions, gray-brown pigment in sun-exposed areas
      • Megaloblastic anemia
      • Neural tube defects (early pregnancy)
      • Homocystinemia increases risk of DVT and atherosclerosis
  • Biotin (B7)
    • Relevant biochemistry pathways
      • Important for carboxylations (pyruvate carboxylase in gluconeogenesis, acetyl CoA carboxylase in fatty acid synthesis, propionyl CoA carboxylase in odd-carbon fatty acids)
    • Causes
      • Excessive consumption of raw eggs (contain avidin, a biotin-binding protein)
      • Biotinidase deficiency
    • Clinical presentation
      • Conjunctivitis, alopecia, eczematous dermatitis