Abstract
Concurrent hemolysis in patients with vitamin B12 deficiency is a well-recognized phenomenon and has been attributed to intramedullary destruction of erythrocytes (ineffective erythropoiesis). Recent studies revealed that homocysteine increased the risk of hemolysis in vitamin B12 deficiency in vitro and there is a high frequency (30%) of vitamin B12 deficiency in asymptomatic patients with homozygous methylene tetrahydrofolate reductase (MTHFR) C677T mutation, a known cause of hyperhomocysteinemia. Here we report three patients with MTHFR mutations and vitamin B12 deficiency presenting with hemolytic anemia and severely elevated homocysteine levels. Patients demonstrated complete resolution of hemolysis with simultaneous normalization of serum homocysteine levels after vitamin B12 treatments. We reviewed pertinent literature, and hypothesized that hemolytic anemia may be more prevalent in patients who have a coexisting MTHFR gene mutation and vitamin B12 deficiency possibly related to severely elevated homocysteine levels. The hemolysis in these cases occurred predominantly in peripheral blood likely due to the combined effects of structurally defective erythrocytes and homocysteine-induced endothelial damage with microangiopathy.
Highlights
Hematological consequences of vitamin B12 deficiency can be severe
We identified three cases of vitamin B12 deficiency and hemolytic anemia associated with severe hyperhomocysteinemia and methylene tetrahydrofolate reductase (MTHFR) gene mutations
While its mechanisms are not entirely understood, it is believed that the hemolysis results from intramedullary destruction [2]
Summary
Hematological consequences of vitamin B12 (cobalamin) deficiency can be severe. It was estimated that 10% of the patients had life threatening conditions such as symptomatic pancytopenia, "pseudo" thrombotic microangiopathy, and hemolytic anemia [1]. The patient was found to have a macrocytic anemia with a slight increase in serum bilirubin levels (2.1 mg/dL) in a screening blood test two weeks prior to admission. The patient was completely asymptomatic 4 months later with the following blood test results: WBC 5,400/mm, http://www.jhoonline.org/content/1/1/26. Vitamin B12 level was 586 pg/mL and his CBC as follows: WBC 5,300, Hb 12.2, and platelet 206,000, which were all within normal ranges. His bilirubin levels were normalized on the follow-up tests after discharge from hospital. One of the patient's sons tested positive for homozygous MTHFR C677T mutation
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