A Rare Autoimmune Hemolytic Overlap: Coombs-Positive Pernicious Anemia

Pernicious anemia is a type of autoimmune disease caused by the presence of anti-intrinsic factor and antiparietal cell antibodies, leading to vitamin B12 deficiency and ineffective erythropoiesis. Autoimmune hemolytic anemia is a variant of anemia in which the direct Coombs test is positive. It is uncommon to find a mixed anemia that has both a pernicious anemia component and an autoimmune anemia component with a positive direct Coombs test, as this association is rarely described. Two cases in which this association was found are presented. The first case involved a 65-year-old woman presenting with profound anemia, macrocytosis, reticulocytosis, elevated lactate dehydrogenase, low haptoglobin, and a positive direct Coombs test. She had anti-intrinsic factor antibodies and responded to vitamin B12 supplementation and corticosteroids. The second case involved an 83-year-old woman with severe anemia, vitamin B12 deficiency, positive antiparietal and anti-intrinsic factor antibodies, and positive direct Coombs test, who similarly improved with cobalamin and immunosuppressive therapy. These cases highlight the rare overlap of pernicious anemia and autoimmune hemolytic anemia, emphasizing the importance of recognizing concurrent autoimmune hemolysis in patients with severe vitamin B12 deficiency to guide prompt and appropriate therapy.