Pseudo-thrombotic Microangiopathy Caused by Acquired Cobalamin Deficiency Due to Unintentional Neglect.

Acquired vitamin B12 (VB12) deficiency is a rare cause of thrombotic microangiopathy (TMA). We experienced an 86-year-old Japanese woman who presented with coma, renal dysfunction, and microangiopathic hemolytic anemia. Although we initially considered thrombotic thrombocytopenic purpura, we eventually diagnosed her to have VB12 deficiency due to inappropriate dietary care based on her low serum VB12 level, social history, and negative parietal cell finding and the presence of intrinsic factor antibody. Because similar cases are expected to increase in today's aging society, our experience underscores the importance of including acquired VB12 deficiency in the differential diagnosis of TMA, even in elderly patients without a history of gastrectomy.