The doctor who stared at schistocytes: an intriguing case of suspected thrombotic microangiopathic anemia.

A 33-year-old man with type 1 diabetes mellitus was admitted to the Internal Medicine Unit due to subacute onset of exertional dyspnea, with evidence at initial blood exams of severe macrocytic anemia with thrombocytopenia, biohumoral signs of hemolysis and 5 schistocytes per magnified field on the blood smear. A thrombotic microangiopathy (TMA) was suspected and plasma exchange (PEX) was started soon, since the risk of a life threatening condition. On the second day, after the results of A Disintegrin And Metalloproteinase with ThromboSpondin-1 motif, member 13 (ADAMTS-13) and reticulocytes were available, a critical reappraisal of the clinical scenario was done. B12 vitamin deficiency was evident after completing the diagnostic work-up. Finally, a diagnosis of "pseudo TMA vitamin B12 deficiency-related" was done. This is an intriguing and rare manifestation of cobalamin deficiency, given the very uncommon occurrence of schistocytes in this condition. "Pseudo TMA vitamin B12 deficiency-related" should be kept in mind when facing the differential diagnosis of microangiopathic anemia in the presence of a low proliferative index.