Langerhans cell histiocytosis (LCH) is a rare disorder that primarily affects children but is also found in adults of all ages. Although some forms of this disease were originally described over a century ago, it has only been recently that LCH has begun to receive more attention, especially in adults. People affected with LCH produce too many dendritic histiocytes, a form of white blood cell found in normal, healthy people and intended to protect the body from foreign materials and infection. In people with LCH, however, these cells multiply excessively and accumulate in certain areas of the body, causing various problems.

Since LCH has been studied over the years, it has acquired several different names as new information was derived about the disease and the syndromes that accompany it. Some of the more common terms previously used to refer to this disorder include histiocytosis X, eosinophilic granuloma, Hand-Schuller-Christian disease, pulmonary histiocytosis, and Letterer-Siwe disease. Other terms which have been used to describe the various syndromes considered to be LCH are reticuloendotheliosis, Hashimoto-Pritzker syndrome, self-healing histiocytosis, pure cutaneous histiocytosis, Langerhans cell granulomatosis, type I histiocytosis, and non-lipid reticuloendotheliosis. Some of these terms may still be used by physicians today to specify the areas of involvement and the course of the disease in individual patients.

Some of the best studies on the incidence of LCH have been done on children with the disease. It is estimated that one in 200,000 children are diagnosed each year. The rarity of LCH in adults makes its incidence difficult to assess, but if we can draw from research which has suggested that a little less than one third of LCH occurs in adults, then about 1 in 560,000 adults might be affected.

Most often an oncologist/hematologist takes the main role in treating patients with LCH. 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 radiologists, surgeons, pulmonologists, dermatologists, dentists, and/or many others to give their input.

Most patients will survive the disease. Some may develop life-long problems while others remain symptom free. In some cases, however, the disease unfortunately may run a progressive course and be life threatening.

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 and/or those who have organ dysfunction. Also, the disease is often more serious if several sites are affected, especially if there is organ dysfunction. Limited involvement can also be serious, depending on the particular site(s) involved, the degree to which the disease continues to progress and involve other vital organs, and the patient's response to treatment.

Overall, physicians will be able to discuss each patient's likelihood of responding and doing well, but patients must understand that it is often difficult for doctors to make definite predictions, because LCH has clearly shown itself to be an unpredictable disease.

The cause of LCH is unknown, although there are some theories which have grown from the research conducted over the past few years. One theory, for example, is that LCH might be triggered by an unusual reaction of the immune system to something commonly found in the environment. Other research has suggested that the disease originates from an inflammatory process. However, even after years of research, the true cause of LCH is still a mystery.

What is known is that LCH is not contagious--patients did not catch it from anyone and cannot infect anyone else with the disease. Furthermore, there is no information to suggest that the disease is hereditary.