Vitamin B12 Deficiency‐Associated Pseudo‐Thrombotic Microangiopathy in a Patient on Longstanding Oral B12 Supplementation

Vitamin B12 deficiency is a common cause of normocytic or megaloblastic anemia. In 2.5% of cases, it can manifest as pseudo‐thrombotic microangiopathy (pseudo‐TMA), which mimics thrombotic thrombocytopenic purpura (TTP), an emergent hemolytic microangiopathy. This case report discusses a stable‐appearing 45‐year‐old female with progressive fatigue, heavy menstrual bleeding, bleeding gums, and easy bruising. Laboratory testing demonstrated low vitamin B12 (121 pg/mL), pancytopenia, exaggeratedly elevated LDH, undetectable haptoglobin, low reticulocyte production index (RPI), and positive intrinsic factor antibody. She was diagnosed with pseudo‐TMA. Unlike TTP, pseudo‐TMA patients often appear clinically well and hemodynamically stable without renal or neurologic dysfunction. Other key differentiators of pseudo‐TMA include progressive anemia, often with irregular red cell morphology; evidence of pancytopenia, neutropenia, and reticulocytopenia; and LDH levels exceeding 2500 units/L. While clinicians should maintain a low threshold for recognizing TTP as a hematologic emergency, they must also maintain awareness of pseudo‐TMA to prevent misdiagnosis and unnecessary plasmapheresis and to optimize treatment.