GSTM1 and microcytic anemia: The mutation activates a cryptic splice site in the mRNA and leads to a reduced expression of the affected β‐globin gene.5 Adult individuals heterozygous for Hb E usually have no clinical symptoms with Hb E ranging from 25% to 35% of the total hemoglobin.6, 7 In an individual with Hb E homozygote, the so‐called Hb EE disease, mild microcytic anemia can be observed.