Langerhans cell histiocytosis (LCH) is a rare disorder that primarily affects children.  The disease was first described in medical literature around the turn of the 20th century. 

A histiocyte is a form of white blood cell.  Its job is to help destroy certain foreign materials and fight infection.  For unknown reasons, patients with this disease have too many histiocytes (Langerhans cells).  These cells accumulate in different organs and can result in a variety of symptoms.

The Histiocytosis Association works closely with an international group of physicians, known as the Histiocyte Society, who are dedicated to studying the histiocytic disorders.  Through this partnership more has been learned and better treatments have been discovered.

Langerhans cell histiocytosis has also been known as Histiocytosis-X, Eosinophilic Granuloma, Letterer-Siwe disease, and Hand-Schuller-Christian Syndrome.

There are also a number of other terms which have been used to describe syndromes which are considered to be Langerhans cell histiocytosis (LCH).  These include: Reticuloendotheliosis, Hasimoto-Pritzker syndrome, Self-healing histiocytosis, Pure cutaneous histiocytosis, Langerhans cell granulomatosis, Type II histiocytosis, and Non-lipid reticuloendotheliosis.

The cause of LCH is unknown.  It may be triggered by an unusual reaction of the immune system from something commonly found in the environment.  It is not a known infection or cancer.  It is not known to be hereditary or communicable.

Over the years, cancer treatments have been used in patients with histiocytosis. Consequently, hematologists and oncologists, who treat cancer, also treat children with Langerhans cell histiocytosis.  However, the disease is not cancer.  Radiation therapy, if used, is given in much lower doses than that which cancer patients receive. 

The vast majority of patients will survive the disease.  Some may develop life-long chronic problems, while others remain symptom free.  In some cases the disease is fatal.  Usually these are very young infants who have a rapid downhill course and do not respond to any known treatment. Whether or not the disease responds to treatment will often depend on the extent of organ involvement; however, it is often difficult to make definite predictions. Physicians will be able to discuss the patient's likelihood of responding to treatment and doing well.

It is estimated that 8.9 of every 1,000,000 children under the age of 15 have histiocytosisSeventy-six (76) percent of the cases occur before ten (10) years of age, but the disease is also seen in adults of all ages.