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.