Hemolysis and schistocytosis in the emergency department: consider pseudothrombotic microangiopathy related to vitamin B12 deficiency

Hemolytic anemia with thrombocytopenia and schistocytosis is suggestive of thrombotic thrombocytopenic purpura (TTP). However, these features can occur in the context of vitamin B12 deficiency. To identify simple means of distinguishing between TTP and pseudothrombotic microangiopathies related to vitamin B12 deficiency (pseudo-TMA) at the bedside. Retrospective study of patients with pseudo-TMA compared with patients with TTP. The patients with pseudo-TMA were further compared with other cases of cobalamin deficiency, in order to detect factors associated with microangiopathic hemolysis during vitamin B12 deprivation. Seven patients with pseudo-TMA were compared with six patients with TTP. The pseudo-TMA patients had higher median lactate dehydrogenase (LDH) levels (7310 vs. 1460 IU/l, P = 0.01), a higher platelet count (73 vs.12.5 × 10(9)/l, P = 0.0023), a lower reticulocyte count (13.1 vs. 265.5 × 10(9)/l, P = 0.0012) and a lower neutrophil count (1.3 vs. 5.1 × 10(9)/l, P = 0.0023). When compared with 21 patients with vitamin B12 deficiency and anemia (but no schistocytosis), the pseudo-TMA patients were more likely to present with pernicious anemia [7 out of 21 (33.3%) vs. 5 out of 7 (71.4%), respectively] and had lower vitamin B12 levels (105 vs. 45 µmol/l, respectively). Vitamin supplementation led to hematological improvements in all pseudo-TMA patients. In a context of mechanical hemolysis with thrombocytopenia in a patient admitted to the emergency department, very high LDH levels and a low reticulocyte count are strongly suggestive of pseudo-TMA and should prompt the physician to screen for cobalamin deficiency.