A person with anaemia has a haemoglobin concentration two standard deviations below the usual range for their age and gender, in men aged over 15 years (Hb below 130 g/L), in non-pregnant women aged over 15 years (Hb below 120 g/L), and in children aged 12-14 years of age (Hb below 120 g/L). The gene discussed is GSTM1; the disease is anemia (phenotype).