College of Medicine, University of Saskatchewan & Saskatoon Cancer Centre, SK, Canada.
Internal Medicine Department, Rheumatology and Clinical Immunology Unit, Faculty of Medicine, Cairo University, Egypt.
Vitam Horm. 2022;119:441-455. doi: 10.1016/bs.vh.2022.01.002. Epub 2022 Feb 25.
Thrombotic microangiopathies (TMAs) are a group of life-threatening conditions requiring urgent management and characterized by a clinical triad of microangiopathic hemolytic anemia, thrombocytopenia, and ischemic tissue injury. Severe vitamin B12 (Cobalamin-Cbl) deficiency or defective cobalamin metabolism, particularly defects in intracellular B12 metabolism, may lead to a TMA-like picture. The latter has been termed metabolism-mediated TMA (MM-TMA). This confusing picture is mediated partly by ineffective erythropoiesis with significant red cell fragmentation resulting in a hemolytic pattern, coupled with reduced platelet production and endothelial injury with organ damage resulting from accumulated toxic byproducts of B12 dysmetabolism. However, unlike in classic thrombotic thrombocytopenic purpura, where therapeutic plasma exchange has to be initiated promptly, cases of MM-TMA can be treated, if diagnosed properly, with adequate B12 replacement.
血栓性微血管病（TMA）是一组危及生命的疾病，需要紧急治疗，其特征是微血管性溶血性贫血、血小板减少和缺血性组织损伤的三联征。严重的维生素 B12（钴胺素-Cbl）缺乏或钴胺素代谢缺陷，特别是细胞内 B12 代谢缺陷，可能导致 TMA 样表现。后者被称为代谢介导的 TMA（MM-TMA）。这种令人困惑的表现部分是由于无效的红细胞生成，导致大量红细胞碎片形成溶血性模式，同时血小板生成减少和内皮损伤，导致 B12 代谢紊乱的毒性副产物堆积，从而导致器官损伤。然而，与必须迅速开始治疗的典型血栓性血小板减少性紫癜不同，如果正确诊断，MM-TMA 病例可以通过适当的 B12 替代治疗。
