8.1: Microangiopathic Hemolytic Anemias (MAHAs)

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https://pressbooks.library.ualberta.ca/mlsci/?p=464

Images of peripheral blood smears demonstrating features of microangiopathic hemolytic anemia . Note the presence of schistocytes, increased polychromasia, and lack of platelets. From MLS Collection, University of Alberta.

Image 1: 50x oil immersion. https://doi.org/10.7939/R3FX74D2V

Image 2: 100 oil immersion. https://doi.org/10.7939/R3B56DK8D

Image 3: 50x oil immersion. https://doi.org/10.7939/R3639KM46

Introduction:^1,2

Microangiopathic hemolytic anemias are a group of disorders that involve the fragmentation of red blood cells in the circulation due to the formation of microthrombi in the microvasculature. This results in intravascular hemolysis and thrombocytopenia.

Red blood cells are physically damaged as they pass through blood vessels resulting in the formation of schistocytes (intravascular hemolysis). The damaged red blood cells are then often removed from circulation by the spleen resulting in extravascular hemolysis.

These features can be found in certain clinical states:

Disseminated Intravascular Coagulation (DIC)
Thrombotic thrombocytopenic purpura (TTP)
Hemolytic-uremic syndrome (HUS)
HELLP Syndrome (Hemolysis, Elevated liver enzymes and Low platelets)

General Laboratory Findings of MAHAs:³

CBC:

PLT: Decreased

Hb: Decreased

RETIC: Increased

PBS:

Schistocytes

Polychromasia

nRBCs

Other Tests:

Unconjugated Bilirubin: Increased

LDH: Increased

Haptoglobin: Decreased

Urine urobilinogen: Increased

Variable hemoglobinuria and hemoglobinemia

References:

1. Smith LA. Hemolytic anemia: nonimmune defects. In: Clinical laboratory hematology. 3rd ed. New Jersey: Pearson; 2015. p.372–87.

2. Harmening DM, Yang D, Zeringer H. Hemolytic anemias: extracorpuscular defects. 5th ed. Philadelphia: F.A. Davis Company; 2009. p. 250-79).

2. Keohane EM. Extrinsic defects leading to increased erythrocyte destruction – nonimmune causes. In: Rodak’s hematology clinical applications and principles. 5th ed. St. Louis, Missouri: Saunders; 2015. p. 394-410.