While some patients with elevated homocysteine levels do not have a complicating hemolytic anemia, as in homocysteinuria and MTHFR gene mutations, the microangiopathic changes in the peripheral blood smears in our cases may be explained by the susceptibility of structurally defective megaloblastic erythrocytes to endothelial damage caused by hyperhomocysteinemia when compared to structurally normal erythrocytes. This evidence concerns the gene MTHFR and hyperhomocysteinemia.