Thanks to future chief Dr. Hossain for a great learning case of a patient with pancytopenia secondary to pernicious anemia resulting in vitamin B12 deficiency.

Key learning points:

• Vitamin B12 (cobalamin) is needed in the formation of hematopoietic cells.
• Deficiency can occur from decreased intake, decreased absorption, or medications.
• Autoimmune pernicious anemia results in impaired vitamin B12 absorption either secondary to blocking intrinsic factor, targeting parietal cells, or both. Look for other associated autoimmune conditions such as thyroid disease or vitiligo
• Labs generally show a macrocytic anemia, however pancytopenia is a common presentation of severe B12 deficiency.
• Intramedullary hemolysis can be seen 2/2 ineffective erythropoiesis.