Paroxysmal Nocturnal Hemoglobinuria and Schistocytes

Pathophysiology and Clinical Significance

Patients with PNH clone size >60% of granulocytes have significantly higher risk of thrombosis and hemolysis, according to the European Association for the Study of the Liver 1
The presence of schistocytes in PNH indicates active intravascular hemolysis, as stated by the International Society on Thrombosis and Haemostasis 4

Microangiopathic hemolytic anemia in PNH is characterized by non-immune hemolytic anemia (negative direct Coombs test), elevated LDH levels, reduced haptoglobin levels, and presence of schistocytes in peripheral blood smear, as reported by the American Society of Hematology 3
Schistocytes may be particularly prominent during acute hemolytic episodes or in patients with concurrent thrombotic complications, according to the European Hematology Association 2

When schistocytes are present along with non-immune hemolytic anemia and thrombocytopenia, it is essential to distinguish between PNH, thrombotic thrombocytopenic purpura (TTP), and atypical hemolytic uremic syndrome (aHUS), as recommended by the American College of Physicians 3
Complete blood count with peripheral blood smear examination to identify schistocytes, and measurement of LDH, haptoglobin, and indirect bilirubin levels are essential for diagnosis, as stated by the International Society for Laboratory Hematology 3

Monitoring for thrombotic complications is essential, as PNH is strongly associated with thrombosis, particularly in unusual sites such as Budd-Chiari syndrome, according to the American Association for the Study of Liver Diseases 1
Regular peripheral blood smear examination to assess for schistocytes and other signs of hemolysis is recommended, as stated by the British Society for Haematology 3