Vitamin B12 deficiency and metabolism-mediated thrombotic microangiopathy (MM-TMA)

Waleed Sabry, Mohamed Elemary, Thierry Burnouf, Jerard Seghatchian, Hadi Goubran

Research output: Contribution to journalReview articlepeer-review

19 Citations (Scopus)


Thrombotic microangiopathies (TMA) are characterized by microangiopathic hemolytic anemia, thrombocytopenia and organ damage resulting from mechanical factors, accumulation of the ultra-large von Willebrand factor multimers or complement-mediated abnormalities. Severe acquired vitamin B12 (Cobalamin - Cbl) deficiency or congenital defective Cbl metabolism could lead to a picture that mimics TMA. The later has been termed metabolism-mediated TMA (MM- TMA). This confusing picture is mediated partly by the large red cell fragmentation coupled with reduced platelet production in the absence of vitamin B12 and partly by the accumulated byproducts and metabolites that induce endothelial injury and hence organ damage. Expensive and complicated treatment for TMA is often initiated on an empiric basis, pending the results of confirmatory tests. In contrast, vitamin B12 Pseudo-TMA and MM-TMA could be treated with proper vitamin B12 supplementation. It is therefore important to identify these disorders promptly. The recent availability of a validated scoring system such as the PLASMIC score uses simple clinical and laboratory parameters. As it incorporates the mean corpuscular volume in its laboratory parameters, this helps in the identification of pseudo and MM-TMA. Perhaps some minor modification of this scoring system by changing the parameters of hemolysis to include reticulocytosis and rather than and/or other hemolytic parameters could even help refine this identification.

Original languageEnglish
Article number102717
JournalTransfusion and Apheresis Science
Issue number1
Publication statusPublished - Feb 2020


  • Cobalamin
  • MM-TMA
  • Plasmic score
  • Thrombotic microangiopathy
  • Vitamin B12

ASJC Scopus subject areas

  • Hematology


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