Abstract
The commonest etiologies of new-onset pancytopenia are congenital bone marrow failure syndromes, marrow space-occupying lesions, infections, and peripheral destruction. Nutritional deficiencies, including folate and vitamin B12, can occasionally cause pancytopenia. We report a 48-year-old gentleman who presented with a 1-week history of dizziness and upper gastrointestinal bleeding. Laboratory evaluation revealed pancytopenia, macrocytosis, toxic neutrophils, hemolysis, suppressed reticulocyte count, positive direct anti-globulin test (DAT), severely reduced B12 levels, and positive anti-intrinsic factor and anti-parietal cell antibodies. He was started on weekly intramuscular B12 supplementation and showed improvement in blood cell counts during follow-up. Recognition of B12 deficiency as a cause of pancytopenia and DAT-positive autoimmune hemolytic anemia can help to avoid unwanted investigations and aid in early diagnosis and treatment.