In vivo and in vitro hemolysis in cold autoimmune hemolytic anemia.

Introduction: Cold-reacting antibodies that bind to and trigger premature erythrocyte destruction are present in patients with cold autoimmune hemolytic anemia (cAIHA). The diagnosis of cAIHA is challenging because of the rarity of the disease, especially in patients with nonspecific features.

Methods: In this case report, we discuss an unusual case of cAIHA in an older man who presented with asymptomatic hyperkalemia, highlighting the hematologic and biochemical changes associated with the disease.

Results: Although hyperkalemia is expected with in vivo hemolysis because of autoantibody-mediated destruction of red blood cells, pseudohyperkalemia caused by in vitro hemolysis was also detected. The combination of actual in vivo hyperkalemia and pseudohyperkalemia resulted in a measured potassium value that was higher than the in vivo potassium concentration.

Discussion: It is pertinent to consider both in vivo and in vitro hemolysis in patients with cAIHA, particularly when assessing potassium status, so that an appropriate intervention can be administered for better patient outcomes.