Langerhans' Cell Histiocytosis (Histiocytosis X)

What Is It?

Langerhans' cells are white blood cells in the immune system that normally play an important role in protecting the body against viruses, bacteria and other invaders. They are found in the skin, lymph nodes, spleen, bone marrow and lungs.

In Langerhans' cell histiocytosis (formerly known as histiocytosis X), Langerhans' cells multiply abnormally. Instead of helping to protect the body, these cells, in massive numbers, cause tissue injury and destruction, especially in the bones, lungs and liver. Although this overgrowth of cells may be like cancer, most researchers do not consider Langerhans' cell histiocytosis to be a form of cancer. In fact, the cells appear to be normal. There are just too many of them. Instead, it seems to be disease of the immune system, in which immune cells multiply abnormally and promote inflammation and damage of surrounding tissues.

Langerhans' cell histiocytosis can develop in only one site or organ, or it can involve several different sites and organs. In most cases, Langerhans' cell histiocytosis that affects many body systems typically occurs in children younger than 2, whereas single-site disease may occur in people of any age.

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