SHM Converge Scientific Abstract ePoster Gallery-B(12) Real: An Unusual Cause of Pancytopenia and Hemolysis

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This case describes a previously healthy 27-year-old man who presented with one week of weakness and orthostatic lightheadedness, along with nausea, vomiting, and diarrhea. Initial evaluation showed severe pancytopenia with macrocytic anemia, neutropenia, and thrombocytopenia, plus laboratory findings concerning for hemolysis: elevated LDH, low haptoglobin, mild indirect hyperbilirubinemia, and a positive direct antiglobulin test (DAT). Because of the severity of the cytopenias, hematologic malignancy and other causes of impaired blood cell production were considered.<br /><br />Peripheral smear demonstrated severe macrocytic anemia with occasional schistocytes and polychromasia. Infectious workup was negative. Further testing revealed an undetectable vitamin B12 level, and the patient was started on intramuscular B12 replacement. He received two units of packed red blood cells and was discharged on oral and weekly IM B12 with hematology follow-up.<br /><br />After discharge, intrinsic factor blocking antibody testing returned positive, confirming pernicious anemia as the cause of his vitamin B12 deficiency. His blood counts and hemolysis markers improved, and the DAT later became negative.<br /><br />The case highlights that severe vitamin B12 deficiency can present not only with macrocytic anemia but also with pancytopenia, neutropenia, and even autoimmune hemolytic anemia-like findings. In young adults, pernicious anemia is an uncommon but important reversible cause. Clinicians should keep vitamin B12 deficiency in the differential when evaluating severe hematologic abnormalities to avoid unnecessary invasive workup and to ensure prompt treatment.

Asset Subtitle

Kate Wimberly

Meta Tag

Author List Kate Wimberly, Rebecca Higdon

Category Clinical Vignettes

Concept Vitamin B12 Deficiency

Concept Pernicious Anemia

Concept Pancytopenia

Concept Neutropenia

Concept Hemolysis

Distinguished Non-Finalist

Presenter Organization University of Kentucky

Presenting Author Kate Wimberly

Track Adult

Keywords

vitamin B12 deficiency

pernicious anemia

pancytopenia

macrocytic anemia

neutropenia

thrombocytopenia

hemolysis

direct antiglobulin test

intrinsic factor antibody

bone marrow failure

Vitamin B12 Deficiency

Pernicious Anemia

Pancytopenia

Neutropenia

Hemolysis