Furthermore, in iron overload patients with increased ferritin (women ≥ 150 to 200 ng/mL and men ≥ 200 to 300 ng/mL) and transferrin saturation ≥ 45%, genetic testing for hereditary haemochromatosis is warranted as erythrocytosis sometimes, yet rarely, appears in haemochromatosis patients [35, 36]. Here, TF is linked to Tangier disease.