Abstract:

This video explains paroxysmal nocturnal hemoglobinuria (PNH), an acquired chronic hemolytic anemia caused by a PI gene mutation in myeloid stem cells. The mutation leads to a deficiency in GPI-anchored proteins like CD55 and CD59, which normally regulate the complement system. Consequently, the alternative complement pathway attacks red blood cells, causing intravascular hemolysis. The video covers the pathogenesis, complications (iron deficiency anemia, acute myeloid leukemia, thrombosis, infection), clinical presentation (hemolytic anemia, pancytopenia, venous thrombosis), diagnostic tests (CBC, LDH, bilirubin, haptoglobin, Coombs test, flow cytometry), and treatment options (iron, folate, RBC transfusion, eculizumab, stem cell transplant).

Paroxysmal Nocturnal Hemoglobinuria: A Comprehensive Overview

• 0:03 Definition: Paroxysmal (episodic/attacks), nocturnal (at night), hemoglobinuria (hemoglobin in urine).

• 0:15 Etiology: Acquired (not inherited) chronic hemolytic anemia due to a mutation in the PI gene of myeloid stem cells.

• 0:39 PI Gene Function: PI gene encodes an enzyme for membrane-associated proteins that regulate the complement system.

• 0:41 Complement Regulation: Glycosylphosphatidylinositol (GPI) anchors complement regulatory proteins (CD55, CD59) to cell membranes. Without GPI, CD55 and CD59 are absent.

• 2:26 Complement System Overview: Complements antibodies, with classical, alternative, and lectin pathways. PNH is primarily related to the alternative pathway.

• 3:03 Alternative Pathway: Triggered by bacterial endotoxin, leading to C3 convertase formation. C3 convertase leads to C5 convertase.

• 3:57 Membrane Attack Complex (MAC): C5b, C6, C7, C8, and C9 form MAC, creating a pore in the cell membrane, disrupting ionic balance and leading to cell lysis.

• 4:29 CD55 and CD59's role: CD55 inhibits C3 convertase; CD59 blocks C9 binding, preventing MAC formation.

• 6:05 PNH Pathophysiology: PI gene mutation causes absent GPI, preventing CD55/CD59 from anchoring to the cell membrane, so the complement system destroys normal blood cells through intravascular hemolysis.

• 6:39 Clinical Presentation:

  • Hemoglobinuria (dark urine, especially in the morning).
  • Complications include iron deficiency anemia, acute myeloid leukemia, thrombosis, and infection.

• 7:54 Triad of Symptoms: Hemolytic anemia, pancytopenia, and venous thrombosis.

• **9 Error: int() argument must be a string, a bytes-like object or a real number, not 'NoneType' (high MCV) is present.

  • Elevated LDH, unconjugated bilirubin, and low haptoglobin (indicators of hemolysis).

• 10:06 Diagnostic Tests:

  • Direct Coombs test is negative.
  • Sucrose hemolysis test is unreliable.
  • Acidified serum test (Ham test) is more reliable for confirmation.
  • Flow cytometry (gold standard): Detects the absence of CD55 and CD59.

• 10:43 Treatment:

  • Iron and folate supplementation.
  • RBC transfusions (if severe).
  • Glucocorticoids are contraindicated.
  • Eculizumab (monoclonal antibody against C5): Prevents C5 cleavage, reducing mortality. Patients must be vaccinated against Neisseria meningitidis.
  • Definitive treatment: Stem cell transplant.

• 11:43 PNH with Aplastic Anemia: Bone marrow transplant is indicated.