AM Report Pearls: RBC-Based Approach to Anemia in Young Person
- When you see anemia in a child or young adult, think of the usual causes of anemia but ALSO think of inherited defects according to the location in the red blood cell
- 1ST LAYER: Membrane defect: e.g. hereditary spherocytosis, hereditary elliptocytosis
- 2nd LAYER: Hemoglobin defect e.g. sickle cell disease, thalassemias
- 3rd LAYER: Enzyme defect e.g. G6PD, pyruvate kinase deficiency
AM Report Pearls: Approach to Hemolytic Anemia
- RBC hemolysis results from damage to the RBC membrane. SEVERE damage leads to intravascularhemolysis. Less severe damage leads extravascular hemolysis.
o Intravascular hemolysis = RBCs lysed within the vasculature!
o Causes include:
- Shearing: MAHAs or defective mechanical heart valves
- Complement mediated destruction: PNH, some drug reactions, ABO incompatibility, rarelyAIHA from cold agglutins (IgM)
- RBCs destroyed in the vasculature–>hemoglobinemia–>hemoglobinuria.. NOT seen in extravascular hemolysis. Chronic heme loss in the urine–>concomitant Fe deficiency anemia!
o Extravascular hemolysis = RBCs destroyed/phagocytosed by macrophages in the liver, spleen, bone marrow, and lymph nodes
o Causes include:
- Immune hemolytic anemia: RBCs coated in IgG, complement, or IgM+complement are phagocytosed in liver, spleen. Partial membrane phagocytosis–>microspherocytes!
- RBC membrane deformities: poorly deformable RBCs get stuck in sinusoids/cords of Billroth then phagocytosed. Ex: hereditary spherocytosis, G6PD def, thalassemia
- All components of RBCs are recycled, including Fe, so you don’t get an Fe deficiency anemia
Hemolysis Labs – seen in intra and extravascular hemolysis
- LDH released from lysed RBCs. Free Hg binds to haptoglobin reducing its serum concentration.
o Combo of increased LDH + reduced haptoglobin = 90 percent specific for diagnosing hemolysis
o Combo of a normal LDH + haptoglobin >25 mg/dL = 92 percent sensitive for ruling out hemolysis
- Direct Antibody Test(Coombs): for immune mediated hemolytic anemia. Detects IgG or complement on RBCs.
o In IgM mediated hemolysis, will only detect complement bound to IgM, not the IgM itself!