[An autopsy case of malignant histiocytosis-like disorder following hypersensitive reaction to mosquito bite].

An autopsy case of an 18-year-old Japanese girl with a malignant histiocytosis-like disorder that developed during the course of a hypersensitive reaction to mosquito bite is reported. Episodes of hypersensitive reactions to mosquito bite had been repeated since she was 12 years old and at the age of 18 years she died of acute respiratory failure only 11 days after a mosquito bite. On autopsy, the dermal reaction to the last mosquito bite had already calmed down, and 'poorly differentiated histiocytes', which were presumed from their histochemical characteristics, had remarkably infiltrated into multiple organs, appearing like leukemic infiltration. Only a small number of them were noted in the lymph nodes and the bone marrow. The results of histochemical examination of 'poorly differentiated histiocytes' was as follows: (1) Neither markers for granulocytes (peroxidase and naphthyl AS-D Cl esterase) nor markers for lymphocytes and plasma cells (leukocyte common antigen and immunoglobulins) were detected. (2) Some markers for histiocytes (peanut lectin agglutinin and lysozyme) were positive in some of the proliferated cells. (3) A marker for T-zone histiocyte (s-100 protein) was negative. These results suggested that the proliferated cells included cells of the monocyte-macrophage system. These cells morphologically showed no phagocytic activity and were suggested to be immature histiocytes. Jurco et al. reported (poorly differentiated) malignant histiocytosis consisting of immature histiocytes without phagocytic activity, by using histochemical methods.(ABSTRACT TRUNCATED AT 250 WORDS)