What is Paroxysmal Nocturnal Hemoglobinuria (PNH)?
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Less common hematologic conditions, their pathophysiology, clinical features, and targeted treatments.
Mastering this deck enables clinicians to recognize and manage rare blood disorders, understand their underlying mechanisms, and implement targeted therapies, improving patient outcomes in complex hematologic cases.
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| # | Front | Back | Hint |
|---|---|---|---|
| 1 | What is Paroxysmal Nocturnal Hemoglobinuria (PNH)? | PNH is a rare acquired stem cell disorder characterized by complement-mediated hemolysis due to deficiency of GPI-anchored proteins that regulate complement activation, leading to intravascular hemolysis, hemoglobinuria, and increased risk of thrombosis. | Think of GPI anchors as protective shields against complement attack. |
| 2 | Which mutation is commonly associated with PNH? | Somatic mutation in the PIGA gene, leading to defective synthesis of GPI anchors on blood cell surfaces. | PIGA mutations disrupt protective surface proteins. |
| 3 | What are the typical clinical features of PNH? | Features include hemolytic anemia (fatigue, pallor), dark-colored urine especially in the morning, thrombosis (particularly atypical sites), and cytopenias. | Hemolysis often worsens at night, hence 'paroxysmal nocturnal'. |
| 4 | How is PNH diagnosed? | Flow cytometry detecting deficiency of GPI-anchored proteins (e.g., CD55, CD59) on blood cells is the gold standard diagnostic test. | Flow cytometry is like a fingerprint test for surface proteins. |
| 5 | What is the primary treatment for PNH? | Complement inhibitor eculizumab, which blocks terminal complement activation, reduces hemolysis and thrombosis risk. | Think of eculizumab as a 'shield' against complement attack. |
| 6 | What are other treatment options besides eculizumab for PNH? | Allogeneic hematopoietic stem cell transplantation in severe cases, and supportive care such as iron supplementation, transfusions, and anticoagulation for thrombosis prevention. | Stem cell transplant can be curative but carries significant risks. |
| 7 | What is the pathophysiology of hemolysis in PNH? | Deficiency of GPI-anchored complement regulatory proteins (CD55, CD59) leads to unregulated complement activation on red blood cells, resulting in intravascular hemolysis. | Loss of protective proteins exposes RBCs to complement attack. |
| 8 | Why are PNH patients at increased risk of thrombosis? | The release of free hemoglobin and hemolysis-related prothrombotic factors, along with platelet activation, contribute to a hypercoagulable state. | Hemolysis can promote clot formation, increasing thrombosis risk. |
| 9 | Name a major complication of untreated PNH. | Severe hemolytic anemia, life-threatening thrombosis, and progression to marrow failure or aplastic anemia. | Untreated PNH can be life-threatening due to clotting and anemia. |
| 10 | What is the difference between PNH and aplastic anemia? | PNH involves hemolysis and thrombosis due to clone expansion of defective stem cells, whereas aplastic anemia primarily involves marrow failure with pancytopenia without hemolysis. | They can coexist but have distinct pathophysiologies. |
| 11 | Which laboratory finding is characteristic of PNH during hemolytic episodes? | Dark urine, especially in the morning, indicating hemoglobinuria, and elevated lactate dehydrogenase (LDH). | Hemoglobin released during intravascular hemolysis causes dark urine. |
| 12 | What is the role of eculizumab in PNH management? | It inhibits the formation of the membrane attack complex (C5), preventing complement-mediated red cell lysis and reducing hemolysis and thrombosis. | Eculizumab acts downstream in the complement pathway. |
| 13 | Name a potential adverse effect of eculizumab therapy. | Increased risk of meningococcal infections due to complement inhibition, requiring vaccination prior to therapy. | Think of eculizumab as suppressing a key part of immune defense. |
| 14 | What distinguishes Cold Hemolytic Disease from PNH? | Cold agglutinin disease involves IgM antibodies causing extravascular hemolysis at low temperatures, whereas PNH involves complement-mediated intravascular hemolysis due to GPI-deficiency. | Temperature dependence helps differentiate these hemolytic processes. |
| 15 | Which other rare blood disorder involves hemolysis but is not related to complement deficiency? | Hereditary spherocytosis, characterized by defected cytoskeletal proteins leading to spherically shaped RBCs and extravascular hemolysis. | Different from PNH, which involves complement-mediated destruction. |
| 16 | What is the significance of thrombosis in PNH patients? | Thrombosis is the leading cause of mortality in PNH, often occurring in atypical sites such as hepatic, portal, or cerebral veins. | A hypercoagulable state heightened by hemolysis. |
| 17 | Can PNH transform into leukemia or marrow failure syndromes? | While rare, PNH clones can coexist or evolve into myelodysplastic syndromes (MDS) or acute myeloid leukemia (AML). | Monitoring for marrow pathology is essential. |
| 18 | How does the flow cytometry test help in diagnosing PNH? | It detects the absence or deficiency of GPI-anchored proteins like CD55 and CD59 on blood cells, confirming PNH clone presence. | Flow cytometry is the diagnostic gold standard. |
| 19 | What is the significance of the 'morning hemoglobinuria' in PNH? | It reflects increased hemolysis during sleep due to complement activation, leading to hemoglobin release that appears in urine upon waking. | Remember: hemoglobinuria often occurs after sleep. |
| 20 | Name another treatment approach for PNH besides complement inhibitors. | Supportive therapies such as transfusions, iron supplementation, and anticoagulation to manage anemia and prevent thrombosis. | Supportive care complements targeted therapies. |
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