Acquired hemolytic anemia can be divided into immune and non-immune mediated forms of hemolytic anemia.
Immune mediated hemolytic anaemia (direct Coombs test is positive)
Autoimmune hemolytic anemia
Warm antibody autoimmune hemolytic anemia
Idiopathic
Systemic lupus erythematosus (SLE)
Evans' syndrome (antiplatelet antibodies and hemolytic antibodies)
Cold antibody autoimmune hemolytic anemia
Idiopathic cold hemagglutinin syndrome
Infectious mononucleosis and mycoplasma (atypical) pneumonia
Paroxysmal cold hemoglobinuria (rare)
Alloimmune hemolytic anemia
Hemolytic disease of the newborn (HDN)
Rh disease (Rh D)
ABO hemolytic disease of the newborn
Anti-Kell hemolytic disease of the newborn
Rhesus c hemolytic disease of the newborn
Rhesus E hemolytic disease of the newborn
Other blood group incompatibility (RhC, Rhe, Kidd, Duffy, MN, P and others)
Alloimmune hemolytic blood transfusion reactions (i.e., from a non-compatible blood type)
Drug induced immune mediated hemolytic anemia
Penicillin (high dose)
Methyldopa
Non-immune mediated hemolytic anemia (direct Coombs test is negative)
Drugs (i.e., some drugs and other ingested substances lead to hemolysis by direct action on RBCs, e.g., ribavirin )
Toxins (e.g., snake venom; plant poisons such as aesculin)
Trauma
Mechanical (from heart valves, extensive vascular surgery, microvascular disease, repeated mechanical vascular trauma)
Microangiopathic hemolytic anemia (a specific subtype with causes such as TTP, HUS, DIC and HELLP syndrome)
Infections (Note: Direct Coombs test is sometimes positive in hemolytic anemia due to infection)
Malaria
Babesiosis
Septicemia
Membrane disorders
Paroxysmal nocturnal hemoglobinuria (rare acquired clonal disorder of red blood cell surface proteins)
Liver disease
Drug induced hemolysis has large clinical relevance. It occurs when drugs actively provoke red blood cell destruction. It can be divided in the following manner:
Drug-induced autoimmune hemolytic anemia
Drug-induced nonautoimmune hemolytic anemia
A total of four mechanisms are usually described, but there is some evidence that these mechanisms may overlap.
