Life-threatening Pseudo-thrombotic Microangiopathy Caused by Severe Vitamin B12 Deficiency

Abstract

Vitamin B12 deficiency is a common cause of macrocytic anemia. Life-threatening hematologic complications including immune and non-immune hemolytic anemia are present in about 10% of the cases. Pseudo-thrombotic microangiopathy is an extremely rare presentation found in around 2.5% of patients with vitamin B12 deficiency. We present a case of a 70-year-old male patient who presented with progressive fatigue and syncope. He was found to severe macrocytic anemia with hemoglobin of 4.1 g/dL. Further workup showed very low serum vitamin B12 level at 22 pg/mL (normal 180-914), methylmalonic acid of 93.23 umol/L (normal 0-0.4) and homocysteine of 93 umol/L (normal 4-12). Anti-parietal cell and intrinsic factor blocking antibodies were positive. He was noted as well to have thrombocytopenia, low haptoglobin, increased lactate dehydrogenase and increased serum creatinine. Peripheral blood smear showed schistocytes, hyper-segmented neutrophils, and marked dimorphic anemia. His presentation was concerning for thrombotic thrombocytopenic purpura; however, PLASMIC score was intermediate. He was monitored in the intensive care unit. He received supportive treatment with intravenous hydration and packed red blood cells transfusion. He was started on daily intramuscular cyanocobalamin supplements. Significant improvement in his symptoms with near normalization of complete blood count after one month of treatment was noted. His condition improved without the need for plasmapheresis.