Case Report: Pernicious anemia-associated pancytopenia responds to immunotherapy

Pancytopenia is a life-threatening condition necessitating a prompt, thorough workup to appropriately treat the underlying pathology. We describe a presentation of pancytopenia attributed to myelodysplastic syndrome (MDS)-associated immune-mediated hemolysis, which initially responded to immunotherapy, including steroids and the anti-CD20 monoclonal antibody rituximab. Cycles of relapse, followed by repeated clinical responses to immunotherapy over a two-year period, supported the diagnosis of immune-mediated cytopenias, substantially delaying identification of the true pathology. Subsequent investigations revealed pernicious anemia as the underlying diagnosis despite ostensibly normal vitamin B 12 levels at presentation. This case highlights how the autoimmune features of pernicious anemia may confound the diagnostic workup of cytopenias by masking the detection of B 12 deficiency, and, surprisingly, result in the sustained response of pernicious anemia to immunotherapy.