Lecture on Anemia

Importance of Anemia in Exams

• Anemia is a common topic in USMLE and COMLEX exams.
• Many types of anemia: microcytic, normocytic, macrocytic.
• Essential to recognize anemia through images and lab findings.

Overview of Anemia

• Anemia Definition: Decreased or hypo-functioning red blood cells or hemoglobin.
• Presentation: Chronic unexplained fatigue.
• Classification: Based on Mean Corpuscular Volume (MCV)
  • Low MCV: < 80
  • Normal MCV: 80-99
  • High MCV: ≥ 100

Low MCV Anemias

1. Iron Deficiency Anemia

   • Most common type of anemia.
   • Often due to bleeding (e.g., colon cancer in older males, menstruation in females).
   • Labs: Low ferritin, high transferrin/TIBC, hypochromia, microcytic RBCs.
   • Association: Plummer-Vinson Syndrome (esophageal webs, iron deficiency anemia, dysphagia).

2. Sideroblastic Anemia

   • Issue with heme production in the porphyrin pathway.
   • Causes include ALA synthetase deficiency, lead poisoning, isoniazid (causes B6 deficiency).
   • Labs: Increased iron and ferritin, decreased TIBC.
   • Key Feature: Ringed sideroblasts (iron buildup in mitochondria, Prussian blue stain).

3. Thalassemia

   • Genetic disorder affecting hemoglobin production (alpha and beta globin chains).
   • Alpha Thalassemia: Varies by number of alpha gene deletions (one deletion to four).
   • Beta Thalassemia: Minor (one gene), Major (two genes, chipmunk facies due to skull deformities).
   • Labs: Varies by type, often confused with other anemias.

Normal MCV Anemias

1. Anemia of Chronic Disease (ACD)

   • Caused by chronic inflammation.
   • Mechanism: Hepcidin reduces iron absorption and increases storage.
   • Labs: Decreased iron and transferrin, increased ferritin.
   • Causes: Chronic infections, kidney disease, autoimmune conditions.

2. Paroxysmal Nocturnal Hemoglobinuria (PNH)

   • Caused by defect in PIGA gene, affecting CD55 and CD59 proteins.
   • Symptoms: Pancytopenia, negative Coombs test, occurs at night ("hibernation").

3. G6PD Deficiency

   • Oxidative stress causes RBC damage due to deficiency in G6PD enzyme.
   • Triggers: Dapsone, sulfa drugs, primaquine, fava beans.
   • Labs: Heinz bodies and bite cells on blood smear.

4. Hereditary Spherocytosis

   • Dysfunction in RBC membrane proteins (spectrin, ankyrin).
   • Symptoms: Splenomegaly, Coombs-negative, increased indirect bilirubin, Howell-Jolly bodies on smear.

High MCV Anemias

1. Vitamin B12 Deficiency

   • Causes include pernicious anemia (autoimmune destruction of gastric parietal cells), ileum dysfunction.
   • Labs: Increased homocysteine and MMA, hypersegmented neutrophils.
   • Symptoms: Neuropsychiatric symptoms, subacute combined degeneration.

2. Folate Deficiency

   • Often nutritional cause (e.g., alcoholism).
   • Labs: Increased homocysteine, normal MMA, hypersegmented neutrophils.

Conclusion

• This lecture covered high-yield types of anemia, their causes, lab findings, and clinical associations.
• For further study, supplement with resources like Pathoma for detailed explanations and additional lower-yield anemias.