Inclusion bodies of aggregated hemosiderins in liver macrophages.

Hemosiderin formation is a structural indication of iron overload. We investigated further adaptations of the liver to excess iron. Five patients with livers showing iron-rich inclusions larger than 2 µm were selected from our database. The clinical features of patients and structures of the inclusions were compared with those of 2 controls with mild iron overload. All patients had severe iron overload with more than 5000 ng/mL of serum ferritin. Etiologies were variable, from hemochromatosis to iatrogenic iron overload. Their histological stages were either portal fibrosis or cirrhosis. Inclusion bodies were ultra-structurally visualized as aggregated hemosiderins in the periportal macrophages. X-ray analysis always identified, in addition to a large amount of iron complexes including oxygen and phosphorus, a small amount of copper and sulfur in the mosaic matrixes of inclusions. There were no inclusions in the control livers. Inclusion bodies, when the liver is loaded with excess iron, may appear in the macrophages as isolated organella of aggregated hemosiderins. Trace amounts of copper-sulfur complexes were always identified in the mosaic matrices of the inclusions, suggesting cuproprotein induction against excess iron. In conclusion, inclusion formation in macrophages may be an adaptation of the liver loaded with excess iron.

Copper Accumulates in Hemosiderins in Livers of Patients with Iron Overload Syndromes.

In biology, redox reactions are essential and sometimes harmful, and therefore, iron metabolism is tightly regulated by cuproproteins. Since the state of copper in iron overload syndromes remains unclear, we investigated whether copper metabolism is altered in these syndromes. Eleven patients with iron overload syndromes participated in this study. The clinical diagnoses were aceruloplasminemia (n=2), hemochromatosis (n=5), ferroportin disease (n=2), and receiving excess intravenous iron supplementation (n=2). Liver specimens were analyzed using a light microscope and transmission electron microscope equipped with an X-ray analyzer. In addition to a large amount of iron associated with oxygen and phosphorus, the iron-rich hemosiderins of hepatocytes and Kupffer cells contained small amounts of copper and sulfur, regardless of disease etiology. Two-dimensional imaging clearly showed that cuproproteins were distributed homogenously with iron complexes within hemosiderins. Copper stasis was unlikely in noncirrhotic patients. The enhanced induction of cuproproteins by excess iron may contribute to copper accumulation in hemosiderins. In conclusion, we have demonstrated that copper accumulates in hemosiderins in iron overload conditions, perhaps due to alterations in copper metabolism.

A male patient with ferroportin disease B and a female patient with iron overload similar to ferroportin disease B.

Reticuloendothelial iron overload is associated with secondary hemochromatosis including repeated transfusions and iron over-supplementation. Ferroportin disease B is a severe subtype of hereditary iron overload syndrome with an activated reticuloendothelial system. The iron exporter ferroportin may be insensitive to hepcidin 25 in this subtype. However, the interactions between the hepcidin-ferroportin system and modifiers of reticuloendothelial iron overload have not yet been elucidated. We describe two patients with iron overload conditions that were compatible with ferroportin disease B, but their genetic backgrounds and habitual states differed. Both patients had diabetes, periportal fibrosis with severe iron deposits in their hepatocytes and Kupffer cells, and adequate levels of circulating hepcidin 25. However, the first patient was heterozygous for a mutation in the FP gene and free from the acquired factors of iron overload, while the second patient was a heavy drinker with a heterozygous mutation in the TFR2 gene and no mutations in the FP gene. The first patient was the second reported case of ferroportin disease B in Japan. Our study on these 2 patients suggests that liver fibrosis associated with compound iron overload of reticuloendothelial cells and hepatocytes may occur via multi-etiological backgrounds.

Measurement of serum hepcidin-25 levels as a potential test for diagnosing hemochromatosis and related disorders.

BACKGROUND: Iron overload syndromes include a wide spectrum of genetic and acquired conditions. Recent studies suggest suppressed hepcidin synthesis in the liver to be the molecular basis of hemochromatosis. However, a liver with acquired iron overload synthesizes an adequate amount of hepcidin. Thus, hepcidin could function as a biochemical marker for differential diagnosis of iron overload syndromes. METHODS: We measured serum iron parameters and hepcidin-25 levels followed by sequencing HFE, HJV, HAMP, TFR2, and SLC40A1 genes in 13 Japanese patients with iron overload syndromes. In addition, we performed direct measurement of serum hepcidin-25 levels using liquid chromatography-tandem mass spectrometry in 3 Japanese patients with aceruloplasminemia and 4 Italians with HFE hemochromatosis. RESULTS: One patient with HJV hemochromatosis, 2 with TFR2 hemochromatosis, and 3 with ferroportin disease were found among the 13 Japanese patients. The remaining 7 Japanese patients showed no evidence for genetic basis of iron overload syndrome. As far as the serum hepcidin-25 was concerned, seven patients with hemochromatosis and 3 with aceruloplasminemia showed markedly decreased serum hepcidin-25 levels. In contrast, 3 patients with ferroportin disease and 7 with secondary iron overload syndromes showed serum hepcidin levels parallel to their hyperferritinemia. Patients with iron overload syndromes were divided into 2 phenotypes presenting as low and high hepcidinemia. These were then associated with their genotypes. CONCLUSION: Determining serum hepcidin-25 levels may aid differential diagnosis of iron overload syndromes prior to genetic analysis.