Anemia Flashcards
- What is macrocytic, microcytic and normocytic RBC anemia usually associated with??
Macrocytic → vit B12 or folic acid deficiency
Microcytic → iron deficiency anemia
Normocytic → acute blood loss
- Discuss the transport and storage of iron in the body.
Ferritin – in intestinal mucosa, liver and heart until body needs it
Transferrin – transporter of iron
- What are the causes of iron deficiency anemia?
- acute or chronic blood loss
- insufficient intake during periods of accelerated growth in children
- heavily menstruating or pregnant women
- Describe the type of anemia caused by iron deficiency.
Hypochromic microcytic anemia
- How is iron deficiency anemia treated?
Oral or parenteral iron preparations
Oral iron therapy → ferrous iron is the most efficiently absorbed therefore ONLY ferrous salts should be used [ferrous sulfate, ferrous gluconate, ferrous fumarate]
Parenteral iron therapy → should be reserved for pts unable to tolerate or absorb oral iron or pts with severe chronic anemia that cannot be maintained with oral iron alone
- What are the adverse effects of oral iron therapy?
- nausea
- epigastric discomfort
- abdominal cramps
- constipation
- diarrhea
* *GI disturbances
- What is acute iron toxicity?
Acute iron toxicity is usually seen in young children who accidently ingest iron tablets. Iron poisoning leads to: necrotizing gastroenteritis, vomiting, abdominal pain, bloody diarrhea leading to shock, metabolic acidosis, coma and death.
- What is the treatment for acute iron toxicity?
Deferoxamine → this is an iron-chelator that binds iron that has already been absorbed to promote its excretion in urine and feces
- What is chronic iron toxicity?
Excess iron is deposited in the heart, liver, pancreas and other organs leading to organ failure and death. This most commonly occurs in patients with inherited hemochromatosis (excessive iron absorption) or pts with repeated transfusions (ex. thalassemia major).
- What is the treatment for chronic iron toxicity?
Phlebotomy OR Deferoxamine or Deferasirox [chelation therapy] may be needed with pts with thalassemia major to stop the accumulation of iron
- What are the active forms and forms found in food of vitamin B12 (cobalamin)?
Active form → deoxyadenosylcobalamin and methylcobalamin
Food form that is converted to active form → cyanocobalamin and hydroxocobalamin (what is also given via vitamin B12 parenteral injection)
*B12 is not synthesized by animals or plants therefore we need to get it from food (meats, eggs, dairy products that have microbially derived vitamin B12). Once consumed, vitamin B12 is stored primarily in the liver.
- How much Vit B12 is needed in the diet?
Only 2 micrograms of Vitamin B12 daily is required in the diet, but the average diet contains 5-30 micrograms of Vitamin B12 daily. The average adult has a total of 3000-5000 micrograms in the total vitamin B12 storage. Because so much more than what is needed is consumed, it would take 5 years for all the stored vitamin B12 to be exhausted and for megaloblastic anemia to develop if B12 absorption were stopped. Although we store so much B12, most vitamin B12 deficiencies in humans result from malabsorption due to lack of intrinsic factor to transporter malfunction. Strict vegetarians who do not eat meat, eggs or dairy products are the ones after many years end up with this vit B12 deficiency.
- Discuss the absorption of vitamin B12.
Vitamin B12 is absorbed only after it complexes with intrinsic factor (glycoprotein secreted by the parietal cells in the gastric mucosa). The IF-vit B12 complex is absorbed in the distal ileum by a receptor-mediated transport system.
- What are the causes of vitamin B12 deficiency?
- pernicious anemia – defective secretion of intrinsic factor [treatment of B12 needs to be given via IV and not orally in these pts if they cannot absorb it]
- Gastrectomy
- Malabsorption syndrome
- IBS
- Small bowel resection
- What enzymatic reactions in the body require vitamin B12?
- Homocysteine → methionine via ______
* Methylcobalamin transfers a methyl group from N5-MTHF to homocysteine. [cobalamin → methylcobalamin via release of methyl group from N5-MTHF to THF – this is a precursor of folate cofactors] Without vitamin B12 the conversion of N5-MTHF (dietary folate) → THF (storage folate) cannot happen - Methylmalonyl-CoA →Succinyl-CoA via methylmalonyl-CoA mutase