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Histiocytosis
Background
Histiocytoses are diseases affecting white blood cells known as histiocytes, which are part of the immune system and, in health, are important in preventing infections. There are several types of histiocyte and therefore several diseases caused by these cells and known as histiocytoses.
Langerhans cell histiocytosis (LCH) is a disease in which cells called Langerhans dendritic cells, accumulate with other immune cells in many parts of the body and cause damage by the release of chemicals. In health, Langerhans cells form a network in the skin and take up foreign materials such as bacteria or viruses that break through the skin surface. The Langerhans cells then move to lymph nodes to start a protective immune response. In the disease, the skin, bone and pituitary gland are commonly affected but the disease may also involve the lungs, intestines, liver, spleen, bone marrow and brain. The disease is found in children and adults but tends to be most severe in very young children.
Haemophagocytic lymphohistiocytosis (HLH) affects histiocytes called macrophages. Affected children have fever, enlargement of the liver and spleen, a fall in the number of normal blood cells, abnormalities of blood clotting and accumulation of macrophages and other white blood cells within affected tissues, typically the bone marrow, liver, spleen and lymph nodes.
Rosai-Dorfman disease, also called sinus-histiocytosis with massive lymphadenopathy, presents with swelling of lymph nodes (typically in the neck), and there may be general ill health with fever and changes in the blood count. The disease is generally self-limiting, but, on occasion, treatment with corticosteroids, cytotoxic drugs, surgery or radiotherapy may be used.
In malignant histiocytosis, some subtypes of acute myeloid leukaemia affect cells of monocyte/macrophage lineage. Other malignant disorders of histiocytes, though, are extremely rare.
