LCH in Adults is a Rare Disorder

LCH occurs when the body produces too many Langerhans cells (histiocytes), which are a type of white blood cell that helps fight infection.
While Langerhans cells are found in normal, healthy people, there is an over-production and build-up of these cells which can lead to organ damage in adults with LCH.
Although some forms of this disease were first described over a century ago, it has only been in recent years that LCH has received more attention, especially in adults.
The name for this disease has evolved over the years, as new information has been discovered. Previously known as Hashimoto-Pritzker syndrome, Letterer-Siwe disease, Hand-Schuller-Christian disease, eosinophilic granuloma and histiocytosis X, the name "Langerhans cell histiocytosis" was later introduced.  This name was agreed upon to recognize the central role of the Langerhans cell.
To date, no large-scale studies have been done on how often LCH occurs in adults.  It is estimated that it occurs in 1-2 adults per million people. It is important to remember that there are still many undiagnosed/misdiagnosed patients.  The length of time from presenting symptoms to diagnosis can be years, which emphasizes the importance of finding a physician who is knowledgeable about this disease.
Information has been collected in various studies, including the 2001 International Histioicyte Society Registry on 274 adults from 13 countries.
In this study, it was reported that 31% of patients had disease in a single system, 68% had more than one system involved , and 30% diabetes insipidus. 
According to another registry based in Germany, it is estimated that 46% of adult patients had bone lesions, 17% skin, 7% pituitary, 4% liver/spleen, 2% brain, and 2% GI tract.
It is estimated that 63% of adults with LCH have lung-only disease, pulmonary Langerhans cell histiocytosis (PLCH), although it can also occur with other involvement, such as bone, skin or diabetes insipidus.
LCH can be systemic, and most often an Oncologist/Hematologist takes the main role in treating patients.  However, since LCH can affect so many areas of the body, sometimes a team approach may be appropriate, and the Oncologist may enlist the help of various types of specialists such as Surgeons, Pulmonologists (lung), Dermatologists (skin), Dentists or Endocrinologists (diabetes/hormones) to give their input.
The patient's chances for survival and maintaining good quality of life depend on the individual case, but research has suggested that the course is less favorable for elderly patients, those with multiple locations of disease and those who may have risk-organ (lungs, liver, spleen, bone marrow) involvement.  Limited involvement can also become serious, depending on the particular sites involved, how quickly the disease continues to progress and the patient's response to treatment.
Overall, physicians will be able to discuss each patients likelihood of responding and doing well, but it is often difficult for doctors to make definite predictions since LCH has clearly shown itself to be an unpredictable disease.
The cause of LCH is unknown, and scientists do not agree on whether LCH is a type of cancer or whether it could be a condition triggered by an inflammatory process.  Genetic predisposing factors are currently being explored.  However, to date, the true cause of LCH remains a mystery.