Intravascular hemolysis occurs in:
PNH is a disease that results from acquired mutations in the phosphatidylinositol glycan complementation group A gene (PIGA), an enzyme that is essential for the synthesis of certain cell surface proteins.
Red cells, platelets, and granulocytes deficient in these GPI-linked factors are abnormally susceptible to lysis by complement. In red cells, this manifests as intravascular hemolysis, caused by the C5b-C9 membrane attack complex.

 

The triad of hemolysis, pancytopenia and thrombosis is unique to PNH.
Thrombosis is the leading cause of disease-related death in PNH.
PNH is best made with flow cytometry in which there is presence of bimodal distribution of the red cells.
Hereditary spherocytosis
Autoimmune haemolytic anemia
Paroxysmal nocturnal hemoglobinuria
Thalassemia