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Histiocytosis
Definition:
Histiocytosis is a generic name for a group of syndromes characterized by an abnormal increase in the number of certain immune cells called histiocyte cells. These include monocytes, macrophages, and dendritic cells. There are 3 major classes of histiocytoses, but this article focuses on Langerhans cell histiocytosis, which is also called histiocytosis X. Text Continues Below
The other 2 classes are non-Langerhans cell histiocytosis (also known as hemophagocytic syndrome) and malignant histiocytosis syndrome (now known as T-cell lymphoma). Alternative Names:
Eosinophilic granuloma; Pulmonary histiocytosis X; Nonlipid reticuloendotheliosis; Pulmonary langerhans cell granulomatosis; Hand-Schuller-Christian disease; Letterer-Siwe disease; Langerhans cell histiocytosis
Causes, incidence, and risk factors:
Most cases of histiocytosis X affect children between ages 1 and 15 years old. The incidence peaks amongst children between 5 and 10. Histiocytosis X is thought to affect roughly 1 in 200,000 people each year. The extra immune cells may form tumors, which can affect various parts of the body. In children, histiocytosis X usually involves the bones (80%) and may consist of single or multiple sites. The skull is frequently affected. The tumors produce a punched-out appearance on bone x-ray. Tumors in weight-bearing bones, such as the legs or spine, may fracture spontaneously. There is often systemic (whole body) involvement as well, causing rashes, lung problems, gum infiltration, lymph gland swelling, hormonal problems, enlargement of the spleen and liver, and anemia. Not surprisingly, with a disease that affects so many systems and organs, histiocytosis may be deadly.
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