Macrocytic Anemia Flashcards
What causes folate deficiency? How long does it take to develop? Where is it absorbed? What are the clinical and laboratory findings?
Poor diet for alcoholics and the elderly, increased demand (pregnancy, cancer, hemolytic anemia) and folate antagonists (methotrexate which inhibits DHF). Absorbed in the jejunum. Develops within months. Clinical findings are
1. Macrocytic RBCs and hyper segmented neutrophils 2. Glossitis 3. Low serum folate 4. High serum homocysteine 5. Normal methylmalonic acid
What are the two causes of macrocytic anemia?
Folate deficiency and vitamin b12 deficiency
Is normal methylmalonic acid found in macrocystic or megaloblastic anemia?
Macrocystic anemia
What are the common causes of vitamin b12 deficiency and what are the clinical and laboratory findings? How long does it take to develop?
Pernicious anemia due to autoimmune destruction of parietal cells leading to intrinsic factor deficiency, pancreatic insufficiency, damage to the terminal ileum via Crohns or diphyllobothrium Latum tapeworm, vegans. Clinical and lab findings are 1. Macrocytic RBCs and hyper segmented neutrophils 2. Glossitis 3. Subacute degeneration of the spinal cord. Takes years to develop due to hepatic stores of B12. 4. Low serum B12 5. High serum homocysteine 6. High methylmalonic acid
Where is vitamin b12 absorbed and how does it get there?
Absorbed in the ileum. Salivary amylase liberates vitamin B12, and bound to R binder and carried to stomach. Pancreatic protease in duodenum detach B12 from R binder. B12 binds intrinsic factor in small bowel and both are absorbed in the ileum.
How does vitamin b12 deficiency cause spinal cord degeneration? Which columns are affected and how does it present ?
Cofactor in the conversion of methylmalonic acid to succinyl CoA and high levels of methylmalonic acid impair spinal cord my elimination. Posterior column damage causes poor proprioception and vibratory sensation and lateral column damage causes spastic paresis.
What does impaired division of RBC precursors cause? Granulocytic precursors?
Megaloblastic anemia. Hyper segmented neutrophils
How are folate and methionine linked? What are causes of non megaloblastic macrocytic anemia?
Folate circulates as methyl THF. Methyl group is transferred to vitamin B12 so folate can participate in DNA precursor activity. b12 transfers methyl group to homocysteine to make methionine. Alcoholism, liver disease, 5 FU.
