Donath-Landsteiner antibody-associated hemolytic anemia after Haemophilus influenzae infection in a child

Role of Complement in Autoimmune Hemolytic Anemia

The classification of autoimmune hemolytic anemias and the complement system are reviewed. In autoimmune hemolytic anemia of the warm antibody type, complement-mediated cell lysis is clinically relevant in a proportion of the patients but is hardly essential for hemolysis in most patients. Cold antibody-mediated autoimmune hemolytic anemias (primary cold agglutinin disease, secondary cold agglutinin syndrome and paroxysmal cold hemoglobinuria) are entirely complement-mediated disorders. In cold agglutinin disease, efficient therapies have been developed in order to target the pathogenic B-cell clone, but complement modulation remains promising in some clinical situations. No established therapy exists for secondary cold agglutinin syndrome and paroxysmal cold hemoglobinuria, and the possibility of therapeutic complement inhibition is interesting. Currently, complement modulation is not clinically documented in any autoimmune hemolytic anemia. The most relevant candidate drugs and possible target levels of action are discussed.

Red blood cell destruction in autoimmune hemolytic anemia: role of complement and potential new targets for therapy

Autoimmune hemolytic anemia (AIHA) is a collective term for several diseases characterized by autoantibody-initiated destruction of red blood cells (RBCs). Exact subclassification is essential. We provide a review of the respective types of AIHA with emphasis on mechanisms of RBC destruction, focusing in particular on complement involvement. Complement activation plays a definitive but limited role in warm-antibody AIHA (w-AIHA), whereas primary cold agglutinin disease (CAD), secondary cold agglutinin syndrome (CAS), and paroxysmal cold hemoglobinuria (PCH) are entirely complement-dependent disorders. The details of complement involvement differ among these subtypes. The theoretical background for therapeutic complement inhibition in selected patients is very strong in CAD, CAS, and PCH but more limited in w-AIHA. The optimal target complement component for inhibition is assumed to be important and highly dependent on the type of AIHA. Complement modulation is currently not an evidence-based therapy modality in any AIHA, but a number of experimental and preclinical studies are in progress and a few clinical observations have been reported. Clinical studies of new complement inhibitors are probably not far ahead.

Florid erythrophagocytosis on the peripheral smear

Erythrophagocytosis is a relatively rare observation on blood smears. It has been reported in auto immune hemolytic anemias and sporadically in few other conditions. Here, we report a case of florid erythrophagocytosis with severe anemia following a viral infection in an 18-year-old girl. Her complete blood count (CBC) revealed hemoglobin of 3.6 gm/dl and a hematocrit of 10%. The peripheral smear showed erythrophagocytosis by neutrophils and rosetting of erythrocytes around neutrophils. The direct Coombs test and direct Donath- Landsteiner tests were positive.

Rituximab as successful therapy in a patient with refractory paroxysmal cold hemoglobinuria

BACKGROUND

Paroxysmal cold hemoglobinuria (PCH) is a rare autoimmune hemolytic anemia (AIHA) attributed to a biphasic hemolysin known as the Donath-Landsteiner (DL) antibody. It is most commonly encountered as an acute transient AIHA after a viral infection in children; the disease resolves after cessation of the infection. The rarest form of PCH is a chronic form in adults that is not (nowadays) associated with infection and is not responsive to conventional therapies. Rituximab has been found to be effective therapy in other forms of AIHA, such as cold agglutinin syndrome, that are refractory to conventional therapies. We describe a case of PCH refractory to steroids that responded to rituximab therapy on two separate occasions.

CASE REPORT

A 64-year-old woman with fatigue was found to be profoundly anemic with laboratory findings consistent with AIHA. She was admitted for the workup and management of her disease after she failed to respond to a course of oral steroids. Laboratory evaluation demonstrated a positive DL test suggesting PCH. She was given a course of rituximab that resulted in normalization of her hemoglobin concentration. She presented 9 months later with recurrent hemolysis. She was given another course of rituximab that again resulted in termination of hemolysis. The patient remained in remission since her last dose of rituximab 19 months previously.

CONCLUSION

To our knowledge, this is the first report of an adult case of refractory PCH successfully treated with rituximab.