Abstract:

This video provides a detailed explanation of Paroxysmal Nocturnal Hemoglobinuria (PNH), a rare acquired hemolytic anemia. It covers the introduction, pathogenesis, clinical features (including the typical triad), lab diagnosis (screening and confirmatory tests), and includes MCQ practice questions. The pathogenesis focuses on the mutation of the GPI gene, leading to a deficiency of CD55 and CD59 (protective guards on blood cells), causing intravascular hemolysis during sleep due to complement activation.

Understanding Paroxysmal Nocturnal Hemoglobinuria (PNH): An Overview

• 0:07 Introduction to PNH: PNH is an acquired hemolytic anemia characterized by defects in the RBC cell membrane.

• 0:52 Pathogenesis - GPI Mutation: The core issue is a mutation in the GPI (glycosylphosphatidylinositol) gene.

• 3:00 Role of CD55 and CD59: Normally, the GPI gene synthesizes CD55 and CD59, two proteins that act as "guards" on blood cells (RBCs, WBCs, platelets). These guards protect cells from lysis by the activated complement system.

• 4:18 PNH Mechanism: In PNH, the mutated GPI gene leads to a deficiency of CD55 and CD59.

• 4:50 Intravascular Hemolysis: Without these protective guards, the activated complement system lyses RBCs, WBCs, and platelets within the blood vessels (intravascular hemolysis).

• 5:09 Hemoglobinuria: The rupture of RBCs releases hemoglobin into the blood, which is then excreted in the urine, causing red-colored urine (hemoglobinuria), especially noticeable in the first morning sample.

• 5:37 PNH – Paroxysmal and Nocturnal Nature: The hemolysis occurs mainly during the night (nocturnal) due to physiological respiratory depression leading to a slightly acidic pH in the blood, which activates the complement system. The anemia is not continuous but occurs in attacks (paroxysmal).

• 8:50 Clinical Features - The Triad: The typical triad of PNH includes:

  • Intravascular Hemolysis: Due to complement-mediated lysis.
  • Pancytopenia: Resulting from the destruction of RBCs (anemia), WBCs (leukopenia), and platelets (thrombocytopenia).
  • Thrombosis: Caused by the absence of CD59 on platelets.

• 10:33 Lab Findings: The findings include hemoglobinemia, hemoglobinuria, mild jaundice, mild anemia, and reticulocytosis.

• 10:52 Screening Test - Ham's Test: An h test is used as a screening test in which RBCs are acidified in vitro. Cells lacking CD55/CD59 will lyse under these conditions.

• 11:48 Confirmatory Test - Flow Cytometry: Flow cytometry is the confirmatory test, detecting the absence of CD55 and CD59 on blood cells. It shows a bimodal distribution of RBCs: some with both CD55/CD59 present and some with both absent.

• 14:37 MCQs: Several MCQs are discussed to solidify understanding of the topic.

• 16:54 Notes Link & Contact: Link for notes and contact number are provided for further assistance.