Case Presentation: A 48 year-old woman with past medical history of Graves’ disease and vitiligo was referred to the emergency department after she presented to clinic with worsening dizziness and generalized malaise over several weeks. She had been lost to follow up and reported not taking any medications. She denied melena, hematochezia, numbness, paresthesias, dyspepsia, chest pain, or shortness of breath. Aside from a mildly low blood pressure of 93/58, vital signs and physical exam were unremarkable. Initial labs revealed pancytopenia with white blood cell count (WBC) of 4.0 (4.8-10.8), hemoglobin (Hgb) 3.8 g/dL (12-16), and platelets 64,000 (130-400). Further work-up before red blood cell transfusion was remarkable for evidence of hemolysis on peripheral blood smear, haptoglobin <10 (45-165), fibrinogen 149 (200-400), and lactate dehydrogenase (LDH) 9231 (140-280). Significantly, vitamin B12 was low at <159.0 pg/mL (200-800), serum methylmalonic acid was high at 8180 nmol/L, and intrinsic factor antibody was positive, which confirmed the diagnosis of pernicious anemia. The patient was started on intramuscular B12 injections and her pancytopenia, hemolysis as well as symptoms quickly improved.

Discussion: Pernicious anemia is an autoimmune disease causing destruction of both gastric parietal cells and the autoantibody inactivation of intrinsic factor leading to malabsorption of vitamin B12. Deficiency of vitamin B12 impairs DNA synthesis, and therefore early recognition and treatment is vital in preventing irreversible cellular damage. The key to diagnosis is often elucidated from laboratory results as patients can be asymptomatic or present with a variety of non-specific symptoms. Our patient did not have the commonly associated megaloblastic anemia, which usually points toward folate or vitamin B12 deficiency, but instead presented with pancytopenia and hemolysis. This phenomenon has been reported in a few, severe cases of B12 deficiency and is thought to be due to ineffective hematopoiesis leading to production of immature cells at risk for cell lysis. After treatment with B12 supplementation, our patient showed improvement in her anemia and degree of hemolysis.

Conclusions: This case highlights the importance of recognizing pernicious anemia as a rare cause of pancytopenia and hemolysis. Early testing should be encouraged as the treatment is simple and procures a good prognosis.