Increased destruction of RBCs due to a defect within the RBC
Extrinsic hemolytic anemia
Abnormal breakdown of normal RBCs
By location of RBC breakdown
Intravascular hemolytic anemia
Increased destruction of RBCs within the blood vessels
Extravascular hemolytic anemia
Increased destruction of RBCs by the reticuloendothelial system (primarily the spleen)
Diagnostics
Indirect (unconjugated) bilirubin
Hemolysis → Hb release → heme catabolized to indirect bilirubin
More prominent in extravascular hemolysis
Heme needs to be catabolized to indirect bilirubin. Macrophages within the reticuloendothelial system (80% in the spleen and 20% in the bone marrow) are predominantly responsible for heme breakdown.
Hemoglobinuria, Hemosiderinuria
More prominent in intravascular hemolysis
Free Hb can’t be catabolized, so they are excreted in urine.
Schistocytes in MAHA or macroangiopathic hemolysis
Intracellular organisms (e.g., in malaria , babesiosis , bartonellosis )
Extravascular hemolysis
↑ Reticulocytes
Spherocytes in hereditary spherocytosis and immune-mediated hemolysis (e.g., warm AIHA, hemolytic transfusion reactions)
Spherocytes are typically found in warm AIHA due to splenic macrophages partially ingesting IgG-coated RBC membranes. A positive DAT and negative family history can distinguish warm AIHA from hereditary spherocytosis.
RBC agglutination in cold agglutinin disease (CAD)
Sickle cells in sickle cell disease
Target cells in HbC disease, Asplenia, Liver disease, Thalassemia
A type of pathologic red blood cell with a bullseye appearance due to an overabundance of membrane.
“HALT,” said the hunter to his target
Teardrop cells in thalassemia
Hb crystals within RBCs in hemoglobin C disease
Smudge cells (Gumprecht shadows) in chronic lymphocytic leukemia (CLL)