52 Paroxysmal Nocturnal Hemoglobinuria (PNH)
Michelle To and Valentin Villatoro
Paroxysmal Nocturnal Hemoglobinuria is an acquired clonal disorder that starts at the stem cell level. Cells produced become susceptible and are destroyed by chronic complement-mediated hemolysis.1,2
Cause(s):1,2
Deficiency in glycosylphosphatidylinositol anchor proteins (GPIs). Normally, CD55 and CD59 act as complement regulators to prevent autologous complement-mediated hemolysis. Without GPIs, cells lack CD55 and CD59 and undergo spontaneous intravascular hemolysis.
Hemolytic episodes (Paroxysms) can be exacerbated by stressors such as inflammation or infections.
Complications:2
Hemolytic Anemia
Bone Marrow Failure
Thrombophilia
Laboratory Results for PNH:1,3,4
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CBC: RBC: Decreased WBC: Decreased PLT: Decreased Hb: Decreased MCV: Increased RETIC: Increased |
PBS: May see: -nRBCs -Polychromasia
If Iron Deficiency Present: -Hypochromic -Microcytic
If Folate Deficiency Present: -Oval Macrocytes
If BM Failure Present: -Pancytopenia |
BM: If BM Failure: -Impaired hematopoiesis -Hypocellular
If not BM Failure, may be: -Normo to hypercellular -Erythroid hyperplasia
Iron stores: Decreased, or absent Note: Any dysplastic findings may be indicative of MDS. |
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Iron Studies: Same as iron deficiency anemia if patient becomes iron deficient. |
Other Tests: Sucrose Hemolysis Test: Positive for hemolysis Ham’s (Acidified Serum Lysis) Test: Positive Flow cytometry (for CD55 and CD59) DAT: Negative Osmotic Fragility: Normal |
Tests for IVH: Indirect bilirubin: Increased Haptoglobin: Decreased LD: Increased Hemoglobinemia Hemoglobinuria Hemosiderinuria |
References:
1. DeZern AE, Brodsky RA. Paroxysmal Nocturnal Hemoglobinuria. A Complement-Mediated Hemolytic Anemia. Hematol Oncol Clin North Am [Internet]. 2015 Jun 7 [cited 2018 Jun 26];29(3):479–94. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4695989/
2. Mastellos DC, Ricklin D, Yancopoulou D, Risitano A, Lambris JD. Complement in paroxysmal nocturnal hemoglobinuria: Exploiting our current knowledge to improve the treatment landscape. Expert Rev Hematol [Internet]. 2014 Oct 2 [cited 2018 Jun 26];7(5):583–98. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4383744/
3. Cochran-Black D. Hemolytic anemia: membrane defects. In: Clinical laboratory hematology. 3rd ed. New Jersey: Pearson; 2015. p. 317-33.
4. Keohane EM. Intrinsic defects leading to increased erythrocyte destruction. In: Rodak’s hematology clinical applications and principles. 5th ed. St. Louis, Missouri: Saunders; 2015. p. 367–93.
