What is (are) Erdheim-Chester disease ?
Erdheim-Chester disease is a rare disorder characterized by histiocytosis, a condition in which the immune system produces excess quantities of cells called histiocytes. Histiocytes normally function to destroy foreign substances and protect the body from infection. Erdheim-Chester disease is classified as a form of non-Langerhans cell histiocytosis to distinguish it from Langerhans cell histiocytosis, which involves accumulation of a specific type of histiocyte called Langerhans cells. In Erdheim-Chester disease, histiocytosis leads to inflammation that can damage organs and tissues throughout the body, causing them to become thickened, dense, and scarred (fibrotic); this tissue damage may lead to organ failure.  People with Erdheim-Chester disease often have bone pain, especially in the lower legs and upper arms, due to an abnormal increase in bone density (osteosclerosis). Damage to the pituitary gland (a structure at the base of the brain that produces several hormones, including a hormone that controls the amount of water released in the urine) may result in hormonal problems such as a condition called diabetes insipidus that leads to excessive urination. Abnormally high pressure of the cerebrospinal fluid within the skull (intracranial hypertension) caused by accumulation of histiocytes in the brain may result in headaches, seizures, cognitive impairment, or problems with movement or sensation. People with this condition can also have shortness of breath, heart or kidney disease, protruding eyes (exophthalmos), skin growths, or inability to conceive a child (infertility). Affected individuals may also experience fever, night sweats, fatigue, weakness, and weight loss.  The signs and symptoms of Erdheim-Chester disease usually appear between the ages of 40 and 60, although the disorder can occur at any age. The severity of the condition varies widely; some affected individuals have few or no associated health problems, while others have severe complications that can be life-threatening.