5.2 Microcytic Anemias Flashcards
What is the MCV in microcytic anemias?
Less than 80
What is the general problem in microcytic anemia?
Decreased production of Hb
What some of the causes of microcytic anemia?
- Fe Deficiency
- Anemia of Chronic Disease
- Sideroblastic (defect of heme synthesis)
- Thalassemia (deficiency of globin)
What is the most common type of anemia?
Fe Deficiency Anemia
Where does Fe absorption occur?
Duodenum
What is the Fe transport molecule?
Transferrin
What is the Fe storage molecule?
Ferritin
What is the common cause of Fe deficiency in an adult male?
Peptic Ulcer Disease
What is the common cause of Fe deficiency in an adult female?
- Menorrhagia
- Pregnancy
What is the common cause of Fe deficiency in an elderly adult?
Colon polyps or carcinoma in the West and Hookworm in 3rd world countries.
What happens to the TIBC as ferritin decreases?
Increases
What are the size of the RBCs in early Fe deficiency?
Normocytic Anemia - RBCs are made normally, but less are made due to deficiency
What are the clinical features of Fe deficiency?
- Anemia
- Koilonychia
- Pica
What will the value of the RDW be in Fe deficiency anemia?
Increased
What is free erythrocyte protoporphyrin?
Free protoporphyrin that is indicative of Fe deficiency anemia due to Fe being decreased but protoporphyrin levels being normal.
What is an associated syndrome with Fe deficiency anemia?
Plummer-Vinson Syndrome
How does Plummer-Vinson Syndrome present?
Presents with anemia, dysphagia and beefy red tongue
What is anemia of chronic disease associated with?
- Chronic Inflammation
- Cancer
How does chronic disease lead to anemia?
Hepcidin sequesters Fe in storage site and limits Fe transfer from macrophages and it decreases EPO production.
What is the function of hepcidin?
Sequesters Fe to prevent access by bacteria - response to inflammation
How can ACD present in its early phase?
Normocytic Anemia
Sideroblastic Anemia
Anemia due to defective protoporphyrin synthesis
What is the rate limiting enzyme in the formation of protoporphyrin?
ALAS - cofactor is Vitamin B6
Where in the cells is Fe attached to protoporphyrin?
Mitochondria
What are the cells seen in sideroblastic anemia?
Ring Sideroblasts - Fe is in the mitochondria
What is the defect in congenital sideroblastic anemia?
Defect in ALAS enzyme
What are some acquired causes of sidroblastic anemia?
- Alcoholism
- Lead Poisoning
- Vitamin B6 Deficiency
What drug can cause Vitamin B6 deficiency?
Isoniazid
Thalassemia
Decreased synthesis of globin chains
What is thalassemia protective against?
Plasmodium falciparum
Components of HbF
alpha2 gamma2
Components of HbA
alpha2 beta2
Components of HbA2
alpha2 delta2
What is the cause of alpha-thalassemia?
Due to a gene deletion - there are normally 4 alpha alleles on Ch16
What happens with 1 alpha gene deletion?
Asymptomatic
What happens with 2 alpha gene deletions?
Mild anemia with slightly increased RBC count
Which deletion of 2 alpha genes is worse, cis or trans?
cis - it is due to an associated with an increased risk of severe thalassemia in offspring
What group is the cis deletion of 2 alpha genes seen more often in?
Asians
What group is the trans deletion of 2 alpha genes seen more often in?
Africans
What happens with 3 alpha gene deletions?
Severe anemia with tetramers of HbH formed from beta chains that damage RBCs
What happens with 4 alpha gene deletions?
Lethal in utero due to hydrops fetalis - gamma chains form tetramers called Hb Barts that damage RBCs
What is the cause of beta-thalassemia?
Mutation of the beta genes on Ch11
Beta Thalassemia Minor
1 normal beta and 1 beta +
- Usually asymptomatic
What cells are seen on smear of beta thalassemia minor?
Target Cells
What is the key lab finding in beta thalassemia minor?
Increased HbA2
Beta Thalassemia Major
2 beta 0
- Most severe and presents with anemia several months after birth as HbF is temporarily protective
What will be seen on x-ray of a patient with beta thalassemia major?
Crew Cut Appearance
What will be seen on blood smear of beta thalassemia major?
Hypochromic Target Cells
What is the key lab finding of beta thalassemia major?
Little to no HbA