Guide to the evaluation of hereditary iron overload. After ruling out acquired causes of hyperferritinemia, TF saturation and clinical phenotype directs further rational genetic evaluation of hereditary iron overload. See text for more details. MAS indicates macrophage activation syndrome; HLH, hemophagocytic lymphohistiocytosis; MDS, myelodysplastic syndrome; LIC, liver iron concentration; and HH, hereditary hemochromatosis.