A 14-year-old boy who presented with debilitating lethargy was shown to have an elevated serum ferritin of 572 mu g/L and a C282Y homozygous HFE genotype. Liver iron concentration was measured non-invasively by magnetic resonance imaging, which revealed a liver iron concentration of 59 mu mol/g dry weight (children's reference range <14). The early phenotypic expression was further investigated by screening genomic DNA for the presence of co-inherited mutations in genes responsible for non-HFE haemochromatosis. Coding regions and splice sites in genes encoding hepcidin and haemojuvelin were sequenced and previously described mutations in ferroportin 1 and transferrin receptor 2 genes were screened. Although no mutations were found, the most likely cause for the early expression is the presence of novel mutations or gene(s).