Hemolysis and Schistocytosis in the Emergency Department: Consider Pseudothrombotic Microangiopathy Related to Vitamin B12 Deficiency

Background: 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.

Aim: To identify simple means of distinguishing between TTP and pseudothrombotic microangiopathies related to vitamin B12 deficiency (pseudo-TMA) at the bedside.

Design And Methods: 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.

Results: 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.

Conclusion: 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.