[Malignant histocytosis].

A case of malignant histiocytosis, a rare disease belonging to the group ofmacrophageal leucoses, was analyzed. Specific clinical symptoms including fever, hepatosplenomegalia, and hematological changes, were noted. The authors adduce the stages of diagnostic search from the onset of the disease to the moment the diagnosis was made, and outline the scope of disease included into differential diagnostics. The errors that led to inappropriate therapeutic tactics and the patient's death are analyzed in the article.