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

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.

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.

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A Laboratory Guide to Clinical Hematology by Michelle To and Valentin Villatoro is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.

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