[Mechanism of hyperferritinemia in a case of malignant histiocytosis]

We report a case of malignant histiocytosis diagnosed by liver-spleen biopsy under laparoscopy. A 49-year-old woman was admitted to our hospital with thrombocytopenia, moderate anemia and hypoproteinemia. Her bone marrow findings revealed erythroid and megakaryocyte hyperplasia, and the serum ferritin concentration was 2,250 ng/ml though she had not received any blood transfusions. Ferrokinetics analysis showed the pattern of ineffective erythropoiesis, and the half-lives of erythrocytes and platelets were both shortened. Her hepatosplenomegaly gradually increased accompanied by increasing serum ferritin level to 10,000 ng/ml. Liver-spleen biopsy was carried out under laparoscopy and revealed infiltration of atypical histiocytes with erythrophagocytosis, which were positive for S-100 and ferritin but negative for lysozyme. The rate of glycosylation in whole serum ferritin, analyzed by using concanavalin-A binding method, showed that her glycosylated ferritin content was only 8.3%, whereas in sera after iron overloading, it was about 70%. Serum isoferritin profiles by isoelectric focussing were studied, and isoferritin pattern from malignant histiocytosis was the same as that in iron overloading after neuraminidase treatment. These findings suggest that serum ferritin is synthesized in proliferating histiocytes and released in the plasma as a nonsecretory type (nonglycosylated ferritin) in this case.