Paroxysmal Nocturnal Hemoglobinuria
Also written as PNH.
*Associated with:* ⭐ - Polycythemia vera - Pregnancy - Post-partum state - Oral contraceptive use - Paroxysmal nocturnal hemoglobinuria (PNH) ⭐ - Intraabdominal cancers, particularly HCC ⭐ - 30% of cases are idiopathic ⭐
What our notes say
- *Associated with:* ⭐ - Polycythemia vera - Pregnancy - Post-partum state - Oral contraceptive use - Paroxysmal nocturnal hemoglobinuria (PNH) ⭐ - Intraabdominal cancers, particularly HCC ⭐ - 30% of cases are idiopathic ⭐ (Liver Histology & Physiology)
- Myelodysplastic syndromes can precede development of AML, as can some cases of myeloproliferative disorders, paroxysmal nocturnal hemoglobinuria, and chemotherapeutic regimens. (hematopathology — Past Paper Questions & Answers)
Practice questions on Paroxysmal Nocturnal Hemoglobinuria
A patient with paroxysmal nocturnal hemoglobinuria (PNH) experiences episodes of red blood cell lysis. This results from:
- Deficiency of C1 inhibitor allowing uncontrolled classical pathway activation
- Deficiency of Factor H causing excessive alternative pathway activity
- Loss of GPI-anchored proteins DAF and CD59 that normally protect cells
- Excessive production of membrane attack complex components
- Antibody-mediated complement activation against RBC antigens
Answer: C. PNH results from acquired deficiency of the enzyme that creates GPI (glycophosphatidylinositol) anchors. This causes loss of GPI-anchored complement regulatory proteins, particularly DAF (decay accelerating factor, which prevents C3 convertase formation) and CD59 (which inhibits MAC formation). Without these protections, complement activation on the patient's own RBCs leads to MAC-mediated cell lysis. RBCs are partic
NOT a typical feature of paroxysmal nocturnal hemoglobinuria?
- Intravascular hemolysis
- Venous thrombosis
- Aplastic anemia
- Positive direct antiglobulin test
- Flow cytometry showing CD55 and CD59 deficiency Answer:
Answer: A. PNH hemolysis is complement-mediated, not antibody-mediated, so DAT is negative.* ---
Which is NOT a typical feature of paroxysmal nocturnal hemoglobinuria (PNH)?
- Intravascular hemolysis
- Venous thrombosis
- Aplastic anemia
- Positive direct antiglobulin test
- Flow cytometry showing CD55 and CD59 deficiency
Answer: D. PNH hemolysis is complement-mediated, not antibody-mediated — so the DAT is characteristically NEGATIVE. ---