Type 4B hereditary hemochromatosis due to heterozygous p.D157A mutation in SLC40A1 complicated with hypopituitarism

Hemochromatosis is a clinical syndrome characterized by iron overload in various organs. We present here a case of type 4 hereditary hemochromatosis due to heterozygous mutation in SLC40A1 gene (p.D157A). SLC40A1 encodes ferroportin, a macromolecule only known as iron exporter from mammalian cells. He first presented symptoms correlated with hypopituitarism. Furthermore, marked hyperferritinemia and high transferrin saturation were revealed in combination with the findings of iron overload in the liver, spleen and pituitary gland by computed tomography and magnetic resonance imaging. Liver biopsy revealed iron deposition in both hepatocytes and Kupffer cells. SLC40A1 mutations are considered to cause wide heterogeneity by various ferroportin mutations. Thus, clinicopathological examinations seem to be very important for diagnosing phenotype of type 4 hemochromatosis in addition to the gene analysis. We diagnosed him as type 4B hereditary hemochromatosis (ferroportin-associated hemochromatosis) by the findings of high transferrin saturation and iron deposition in hepatocytes, and then started iron chelating treatment. We should suspect the possibility of hereditary hemochromatosis even in Japanese with severe iron overload. Although the same mutation in SLC40A1 gene (p.D157A) had been reported to cause "loss of function" phenotype, we considered that the mutation of our case caused "gain of function" phenotype.