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Vitamin C deficiency

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Vitamin C deficiency- Causes, clinical manifestations, laboratory diagnosis and treatment.

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Vitamin C deficiency

  1. 1. By- Professor (Dr.) Namrata Chhabra Biochemistry For Medics - Lecture Notes www.namrata.co 8/30/2014 1 Biochemistry For Medics
  2. 2.  Vitamin C (ascorbic acid) plays a role in collagen, carnitine, hormone, and amino acid formation.  It is essential for wound healing and facilitates recovery from burns.  Vitamin C is also an antioxidant, supports immune function, and facilitates the absorption of iron. 8/30/2014 2 Biochemistry For Medics
  3. 3.  Scurvy is caused by a dietary deficiency of vitamin C.  The body's pool of vitamin C can be depleted in 1-3 months.  Risk factors include the following: Babies who are fed only cow's milk during the first year of life are at risk. Alcoholism Elderly individuals who eat a tea-and-toast diet Retired people who live alone and those who eat primarily fast food 8/30/2014 3 Biochemistry For Medics
  4. 4. Economically disadvantaged persons tend to not purchase foods high in vitamin C (eg, green vegetables, citrus fruits), which results in them being at high risk. Vitamin C deficiency has been noted in refugees who are dependent on external suppliers for their food and have limited access to fresh fruits and vegetables. 8/30/2014 4 Biochemistry For Medics
  5. 5. Cigarette smokers require increased intake of vitamin C because of lower vitamin C absorption and increased catabolism. Pregnant and lactating women and those with thyrotoxicosis require increased intake of vitamin C because of increased utilization. 8/30/2014 Biochemistry For Medics 5
  6. 6. People with anorexia nervosa or anorexia from other diseases such as AIDS or cancer are at increased risk of vitamin C deficiency. People with type 1 diabetes have increased vitamin C requirements, as do those on hemodialysis and peritoneal dialysis. Biochemistry For Medics 8/30/2014 6
  7. 7. Because vitamin C is absorbed in the small intestine, people with disease of the small intestine such as Crohn’s, Whipple, and celiac disease are at risk. Iron overload disorders may lead to renal vitamin C wasting. Biochemistry For Medics 8/30/2014 7
  8. 8. Biochemistry For Medics 8/30/2014 8
  9. 9.  Vitamin C is functionally most relevant for the triple-helix formation of collagen; a vitamin C deficiency results in impaired collagen synthesis.  Proline and lysine hydroxylases are required for the post synthetic modification of procollagen to collagen.  Vitamin C is necessary as a coenzyme for these hydroxylases. Biochemistry For Medics 8/30/2014 9
  10. 10. Biochemistry For Medics 8/30/2014 10
  11. 11.  Formation of intercellular cement substances in connective tissues, bones, and dentin is defective, resulting in weakened capillaries with subsequent hemorrhage and defects in bone and related structures.  Hemorrhaging is a hallmark feature of scurvy and can occur in any organ.  Hair follicles are one of the common sites of cutaneous bleeding Biochemistry For Medics 8/30/2014 11
  12. 12.  Bone tissue formation becomes impaired, which, in children, causes bone lesions and poor bone growth.  Fibrous tissue forms between the diaphysis and the epiphysis, and costochondral junctions enlarge.  Densely calcified fragments of cartilage are embedded in the fibrous tissue. Biochemistry For Medics 8/30/2014 12
  13. 13.  Subperiosteal hemorrhages, sometimes due to small fractures, may occur in children or adults. Biochemistry For Medics 8/30/2014 13
  14. 14.  Early symptoms are malaise and lethargy.  After 1-3 months, patients develop shortness of breath and bone pain.  Myalgias may occur because of reduced carnitine production.  Other symptoms include skin changes with roughness, easy bruising and petechiae, gum disease, loosening of teeth, poor wound healing, and emotional changes. Biochemistry For Medics 8/30/2014 14
  15. 15.  Dry mouth and dry eyes  In the late stages, jaundice, generalized edema, oliguria, neuropathy, fever, and convulsions can be seen.  Vital signs: Hypotension may be observed late in the disease. This may be due to an inability of the resistance vessels to constrict in response to adrenergic stimuli. Biochemistry For Medics 8/30/2014 15
  16. 16.  Skin: Perifollicular hemorrhages (See figure),purpura, and ecchymoses are seen most commonly on the legs and buttocks where hydrostatic pressure is the greatest.  Poor wound healing and breakdown of old scars may be seen. Biochemistry For Medics 8/30/2014 16
  17. 17. Nails: Splinter hemorrhages may occur. Biochemistry For Medics 8/30/2014 17
  18. 18. Head and neck:  Gum swelling, friability, bleeding, and infection with loose teeth;  mucosal petechiae; Biochemistry For Medics 8/30/2014 18
  19. 19.  Scleral icterus (late, probably secondary to hemolysis); and pale conjunctiva are seen.  Conjunctival hemorrhage,  Bleeding into the periorbital area, eyelids, and retrobulbar space also can be seen.  Alopecia may occur secondary to reduced disulfide bonding. Biochemistry For Medics 8/30/2014 19
  20. 20. Biochemistry For Medics 8/30/2014 20
  21. 21. Chest and cardiovascular:  Scorbutic rosary (ie, sternum sinks inward) may occur in children.  High-output heart failure due to anemia can be observed.  Bleeding into the myocardium and pericardial space has been reported. Biochemistry For Medics 8/30/2014 21
  22. 22.  Extremities:  Fractures, dislocations, and tenderness of bones are common in children.  Bleeding into muscles and joints may be seen.  Edema may occur late in the disease.  Gastrointestinal: Loss of weight secondary to anorexia is common. Biochemistry For Medics 8/30/2014 22
  23. 23. Diagnosis is usually made clinically in a patient who has skin or gingival signs and is at risk of vitamin C deficiency are normal Laboratory Investigations A plasma or leukocyte vitamin C level can confirm clinical diagnosis. Scurvy occurs at levels generally less than 0.1 mg/dL. Symptoms occur at levels below 2.5 mg/L, which is considered deficiency. Levels of 2.5-5 mg/L indicate depletion. Levels can be low in patients who have tuberculosis, rheumatic fever, or other chronic illnesses; those who smoke cigarettes; and patients on oral contraceptive drugs. Biochemistry For Medics 8/30/2014 23
  24. 24.  Capillary fragility can be checked by inflating a blood pressure cuff and looking for petechiae on the forearm.  Bleeding time, clotting time and Prothrombin are estimated to rule out other bleeding disorders Biochemistry For Medics 8/30/2014 24
  25. 25.  An Fe deficiency anemia is generally observed.  Vitamin C enhances the absorption of iron from the small intestine.  This may contribute to the anemia seen with vitamin C deficiency. Biochemistry For Medics 8/30/2014 25
  26. 26.  Loss of trabeculae results in a ground-glass appearance.  The cortex thins.  A line of calcified, irregular cartilage (white line of Fraenkel) may be visible at the metaphysis.  The epiphysis may be compressed. Biochemistry For Medics 8/30/2014 26
  27. 27.  In adults, scurvy must be differentiated from  Arthritis, Hemorrhagic disorders,  Gingivitis, and  Protein-energy malnutrition. Biochemistry For Medics 8/30/2014 27
  28. 28.  Patients should take ascorbic acid at 100 mg 3-5 times a day until total of 4 g is reached, and then they should decrease intake to 100 mg daily.  Divided doses are given because intestinal absorption is limited to 100 mg at one time.  Parenteral doses are necessary in those with gastrointestinal malabsorption. Biochemistry For Medics 8/30/2014 28
  29. 29.  Diet  Foods high in vitamin C include the following. Citrus fruits, especially grapefruits and lemons Vegetables, including broccoli, green peppers, tomatoes, potatoes, and cabbage Biochemistry For Medics 8/30/2014 29
  30. 30.  The recommended daily allowance for vitamin C varies.  The current recommendation for adults is 120 mg daily, although a dose of 60 mg daily is all that is required to prevent scurvy.  Diets high in vitamin C have been claimed to lower the incidence of certain cancers, particularly esophageal and gastric cancers Biochemistry For Medics 8/30/2014 30
  31. 31. Taking >2 g of vitamin C in a single dose may result in- Abdominal pain, Diarrhea, and nausea. Since vitamin C may be metabolized to oxalate, it is feared that chronic, high-dose vitamin C supplementation could result in an increased prevalence of kidney stones, thus it is reasonable to advise patients with a past history of kidney stones to not take large doses of vitamin C. There is also an unproven but possible risk that chronic high doses of vitamin C could promote iron overload in patients taking supplemental iron. Biochemistry For Medics 8/30/2014 31
  32. 32. Vitamin C deficiency can occur as part of general under nutrition, but severe deficiency (causing scurvy) is uncommon.  Symptoms include fatigue, depression, and connective tissue defects (eg, gingivitis, petechiae, rash, internal bleeding, impaired wound healing). In infants and children, bone growth may be impaired. Severe deficiency results in scurvy, a disorder characterized by hemorrhagic manifestations and abnormal osteoid and dentin formation. Diagnosis is usually clinical. Treatment consists of oral vitamin C. Biochemistry For Medics 8/30/2014 32

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