Hemolysis Basics
This classic lab triad confirms active red cell destruction: LDH ↑, haptoglobin ↓, and indirect bilirubin ↑.
What is the hemolysis triad?
Sickle cell disease results from this beta-globin point mutation: glutamic acid is replaced by this amino acid at codon 6.
What is valine?
Unlike sickle cell disease, thalassemia is a problem of globin-chain quantity rather than this.
What is globin-chain quality / structure?
This X-linked RBC enzyme deficiency causes episodic hemolysis after infection, fava beans, or oxidant drugs.
What is G6PD deficiency?
A positive DAT means this is coating the patient’s RBC surface in vivo.
What are antibodies and/or complement?
This site of hemolysis produces free plasma hemoglobin, hemoglobinuria, dark urine, and very high LDH.
What is intravascular hemolysis?
Dehydration, infection, hypoxia, cold exposure, and stress are classic triggers for this painful SCD complication
What is vaso-occlusive crisis?
This smear clue is common in thalassemia and resembles a bullseye.
What are target cells?
These two smear findings suggest oxidative hemolysis from G6PD deficiency.
What are bite cells and Heinz bodies?
DAT positive for C3, RBC agglutination, and symptoms worsened by cold exposure point to this diagnosis.
What is cold agglutinin disease?
This site of hemolysis is mediated by splenic/hepatic macrophages and commonly produces jaundice and splenomegaly.
What is extravascular hemolysis?
In infants with SCD, painful swelling of the hands and feet as HbF declines is called this
What is dactylitis / hand-foot syndrome?
Deletion of three alpha-globin genes produces this alpha-thalassemia phenotype.
What is Hemoglobin H disease?
G6PD enzyme testing during an acute crisis can be falsely normal because these cells remain in circulation.
What are young reticulocytes / younger RBCs with higher enzyme activity?
Warm AIHA commonly produces this smear finding, which can also appear in hereditary spherocytosis.
What are spherocytes?
This test helps separate immune-mediated hemolysis from nonimmune/congenital hemolysis.
What is the direct antiglobulin test / DAT / direct Coombs test?
This chronic SCD medication raises fetal hemoglobin and reduces vaso-occlusive crises.
What is hydroxyurea?
Deletion of all four alpha-globin genes produces this fatal fetal condition.
What is Hb Bart’s / alpha-thalassemia major / hydrops fetalis?
Because mature RBCs lack mitochondria, interruption of glycolysis in this disorder causes ATP failure and chronic hemolysis.
What is pyruvate kinase deficiency?
Schistocytes plus thrombocytopenia should trigger concern for this emergency hemolysis category.
What is MAHA / microangiopathic hemolytic anemia?
A urine dipstick is positive for heme, but microscopy shows no intact RBCs. This finding points to this process.
What is hemoglobinuria from intravascular hemolysis?
Recurrent splenic infarctions in HbSS cause this chronic complication, increasing risk from encapsulated bacteria
What is functional asplenia / autosplenectomy?
Beta-thalassemia major requires regular transfusions, creating this major long-term treatment threat.
What is iron overload requiring chelation?
The gold-standard test for PNH detects loss of these two complement-regulating proteins.
A 19-year-old develops sudden jaundice and cola-colored urine 2 days after starting TMP-SMX for a skin infection. Labs show anemia, LDH ↑↑, haptoglobin ↓, indirect bilirubin ↑, and reticulocytosis. Smear shows bite cells and Heinz bodies. DAT is negative. Name the diagnosis AND the key testing pitfall.
What is G6PD deficiency, and do NOT rely on G6PD enzyme testing during the acute hemolytic crisis because it may be falsely normal?