Microcytic Anemias Flashcards
https://www.youtube.com/watch?v=e97QOkEvhrc&t=1491s
What is the most common type of anemia?
Iron-deficiency anemia
What are microcytic anemias (MCV <80) usually due to?
Lack of hemoglobin production
- Iron deficiency
- Defect in heme group / protoporphyrin ring synthesis (Sideroblastic anemia)
- Defect in the heme protein itself (Thalassemias)
- Anemia of chronic disease (Can also be normocytic)
What are normocytic anemias (MCV 80 - 99) usually due to?
- Anemia of chronic disease
- Paroxysmal nocturnal hemoglobinuria
- G6PD Deficiency
- Hereditary spherocytosis
What are macrocytic anemias (MCV >100) usually due to?
- B12 deficiency (Malnutrition, chronic gastritis, pernicious anemia)
- Folate deficiency (Malnutrition, alcoholism, chemotherapy)
What is a likely cause of iron-deficiency anemia in an older man?
Colon cancer and colorectal bleeding (Until proven otherwise)
What labs are seen in iron-deficiency anemia?
Low ferritin (Iron-storage protein)
High transferrin / total iron-binding capacity
Hypochromic (Pale RBCs)
Microcytic
What anemia is associated with Plummer-Vinson Syndrome?
Iron-deficiency anemia (Along with esophageal webs and dysphagia)
What do hypochromic RBCs look like?
What is sideroblastic anemia?
A microcytic anemia resulting from an abnormality in heme production in the porphyrin pathway.
What is the most common cause of sideroblastic anemia?
What are some other causes?
ALA synthetase deficiency
- Lead poisoning*
- Administration of certain medications (E.g. isoniazid)*
What happens with Fe2+ and heme in the mitochondria?
What happens during sideroblastic anemia?
Fe2+ and heme are joined in the mitochondria.
In sideroblastic anemia, we have a heme deficiency, and so Fe2+ builds up in the mitochondria.
What enzymes in heme synthesis are inhibited in lead poisoning?
ALA dehydratase
Ferrochetalase
How does isoniazid (TB antibiotic) cause sideroblastic anemia?
Isoniazid inhibits vitamin B6 (which is a cofactor in ALA synthase activity)
What can Prussian blue be used to stain in the cell?
Iron (Especially in sideroblastic anemia)
What are the lab results for sideroblastic anemia?
Increased iron
Increased ferritin
Decreased total iron-binding capacity / transferrin
What are the thalassemias?
Microcytic anemias caused by an abnormality in hemoglobin synthesis (The peptide itself) due to a deletion in the gene.
How many alpha and beta genes are there for thalassemia?
4 alpha
2 beta
What is the impact of different amounts of alpha deletions in thalassemia?
1 deletion - Asymptomatic
2 deletions - mild anemia
3 deletions - severe anemia
4 deletions - hydrops fetalis
Is there a difference in mild (2 deletions) alpha-thalassemias by race?
Asian –> CIS deletion (Both on same chromosome)
African –> TRANS deletion (On different chromosomes)
What is the impact of a different number of mutations in beta-thalassemia?
1 deletion - beta-thalassemia minor (Mostly asymptomatic)
2 deletions - beta-thalassemia major (Chipmunk facies and crew cut skull x-ray)
Why does beta-thalassemia major result in chipmunk facies and a crew cut appearance on X-ray?
Extramedullary hematopoiesis (The body is trying to compensate for decreased erythropoeisis by stimulating RBC production in other bones; e.g. the skull and face)
What type of hemoglobin is elevated in beta-thalassemia major?
Hemoglobin A2
What is anemia of chronic disease?
Anemia due to an underlying, chronic inflammation
What acute inflammatory product is involved in anemia of chronic disease? What is the mechanism of action?
Hepcidin; inflammation triggers hepcidin to decrease gut iron absorption and increase iron storage by ferritin
What labs are associated with anemia of chronic disease?
Decreased iron
Increased ferritin
Decreased total iron-binding capacity / transferrin
What are three non-infectious diseases that are commonly associated with anemia of chronic disease?
Kidney disease
Autoimmunity
Rheumatologic diseases
