Case Presentation: 58 year old African-American female child-care worker with history of GERD presented with symptomatic anemia. She was in her usual state of health until ten days prior to presentation, when she had several days of GI illness consisting of abdominal pain and diarrhea. Her symptoms self-resolved, only with residual mild epigastric abdominal pain. However, a few days later she experienced fatigue, lightheadedness, and exercise intolerance. She denied any GI bleeding and was post-menopausal without any recent GU bleeding.
Vital signs were normal and labs revealed a normocytic nonproliferative anemia with hematocrit 15.9 and reticulocyte index 0.06. LDH was 20,586, haptoglobin 20, and total bilirubin 1.7. Rest of labs showed WBC 3.4, Plt of 210, normal electrolytes and iron studies, and AST 185/ALT 81. Direct Coombs, G6PD, parvovirus, EBV, and CMV were negative. Peripheral smear showed no schistocytes and numerous teardrop cells. CT scan was negative for lymphoma.

She was initially treated empirically for Coombs-negative autoimmune hemolytic anemia with oral glucocorticoids – however, her LDH continued to increase to 23,000 with low reticulocyte index. Vitamin B12 was low at 159 and bone marrow was markedly hypercellular with erythrocytic hyperplasia, moderate megaloblastic and dysplastic maturation, and granulocytes with megaloblastic features. Homocysteine and methylmalonic acid were elevated. She was started on vitamin B12 with near-immediate decrease in her LDH and recovery of her reticulocyte index to 7.5. She was discharged with vitamin B12 supplementation and anti-intrinsic factor antibodies checked after discharge were positive.

Discussion: The differential diagnosis in this case was very broad and included viral (including parvovirus), autoimmune (warm-antibody autoimmune hemolytic anemia, pernicious anemia), consumptive (microangiopathic hemolytic anemia), and lymphoproliferative. With initial labs suggestive of hemolysis, the patient was started on corticosteroids until further workup supported pernicious anemia.

Vitamin B12 deficiency is a well-known yet relatively uncommon cause of anemia in the developed world. It is unusual to have dietary B12 deficiency – more commonly it is caused by pernicious anemia, an autoimmune gastritis resulting in destruction of intrinsic factor and/or gastric parietal cells. The patient described in the case did have chronic GERD symptoms, although it is unclear whether her recent GI illness was related to her anemia.

Elevated LDH/bilirubin and low haptoglobin are typically associated with intravascular hemolytic anemias. However, patients with vitamin B12 deficiency commonly have intramedullary hemolysis caused by cell-precursor destruction in response to ineffective hematopoiesis. Therefore, B12 deficiency can be initially mistaken for intravascular causes of hemolytic anemia such as microangiopathic or autoimmune hemolysis. The reticulocyte index can be used to distinguish these – intravascular hemolytic anemias are proliferative, while B12 deficiency causes a nonproliferative hemolysis.

Conclusions: Vitamin B12 deficiency caused by pernicious anemia can mimic intravascular hemolytic anemias. Intramedullary hemolysis due to ineffective hematopoiesis can lead to markedly elevated LDH levels (>23,000 in this case) with low haptoglobin and elevated bilirubin. However, a key distinguishing characteristic is that intramedullary hemolysis due to B12 deficiency will result in a low reticulocyte count.