The WHO further categorizes anemia severity into three levels: Mild anemia, with Hb levels between 10 and 10.9 g/dL; Moderate anemia, with Hb levels between 7 and 9.9 g/dL; and Severe anemia, with Hb levels below 7 g/dL [13]. The gene discussed is GSTM1; the disease is anemia (phenotype).