Metabolism-Mediated Thrombotic Microangiopathy in an Older Patient Without Malnutrition.

Vitamin B12 deficiency can cause thrombotic microangiopathy (TMA)-like symptoms such as purpura caused by platelet reduction, general fatigue caused by anemia, and renal and hepatic abnormalities caused by malnutrition. TMA-like symptoms are known as metabolism-mediated TMA (MM-TMA). In MM-TMA, blood cell production is altered, and both pancytopenia and schistocytes appear. The initial presentation of MM-TMA makes it challenging to distinguish between primary and secondary TMA when patients do not present risk factors for malnutrition. We encountered an older female patient with a chief complaint of unconsciousness and loss of appetite for two days. Laboratory tests revealed pancytopenia with schistocytes. Moreover, the laboratory data revealed low serum levels of vitamin B12, indicating MM-TMA. The patient was successfully treated with intravenous vitamin B12 supplementation and discharged home. The patient had atrophic gastritis, which could have impeded the absorption of vitamin B12 from food. Among older patients without prolonged appetite loss, TMA-like symptoms should be investigated as MM-TMA induced by vitamin B12 deficiency, and prompt initiation of appropriate treatment is essential to differentiate between MM-TMA and true TMA.