- A rare but potentially deadly disorder with similarities to cancer, in which histiocytes start to multiply and attack the person’s own tissues or organs. The result can be tissue damage, pain, development of tumor-like lumps called granulomas, fatigue, and other symptoms. If histiocytosis affects the pituitary gland, diabetes insipidus may also develop. Treatment is by radiation and chemotherapy, although for reasons unknown, some cases go into remission without treatment.
* * *- Langerhans cell h. a set of closely related disorders unified by a common proliferating element, the Langerhans cell. Three overlapping clinical syndromes are recognized: a single site disease (eosinophilic granuloma), a multifocal unisystem process (Hand-Schuller-Christian syndrome), and a multifocal, multisystem h. (Letter-Siwe syndrome.) Formerly this process was known as h. X. SYN: h. X.- lipid h. h. with cytoplasmic accumulation of lipid, either phospholipid (Niemann-Pick disease) or glucocerebroside (Gaucher disease).- malignant h. a rapidly fatal form of lymphoma, characterized by fever, jaundice, pancytopenia, and enlargement of the liver, spleen, and lymph node s; the affected organs show focal necrosis and hemorrhage, with proliferation of histiocytes and phagocytosis of red blood cells.- nonlipid h. SYN: Letterer-Siwe disease.- sinus h. with massive lymphadenopathy a chronic disease occurring in children and characterized by massive painless cervical lymphadenopathy due to distension of the lymphatic sinuses by macrophages containing ingested lymphocytes, and by capsular and pericapsular fibrosis. SYN: Rosai-Dorfman disease.- h. Y SYN: verrucous xanthoma.
* * *his·tio·cy·to·sis -'tō-səs n, pl -to·ses -.sēz abnormal multiplication of macrophages <Langerhans cell \histiocytosis> broadly a condition characterized by such multiplication
* * *n.any of a group of diseases in which there are abnormalities in certain large phagocytic cells (histiocyte) due to (1) abnormal storage of fats, as in Gaucher's disease; (2) inflammatory disorders, as in Langerhans cell histiocytosis, which includes disorders previously called histiocytosis X; or (3) malignant proliferation of histiocytes.
* * *his·tio·cy·to·sis (his″te-o-si-toґsis) any of a variety of proliferative disorders of macrophages (histiocytes), marked by the abnormal appearance of macrophages in the blood, or by abnormally elevated numbers of macrophages in lymphoid tissue.
Medical dictionary. 2011.