Children's Hospital Colorado

Langerhans Cell Histiocytosis

What is Langerhans cell histiocytosis?

Langerhans cell histiocytosis (LCH) happens when part of the immune system stops working the way it should. The term “histiocytosis” comes from the word “histiocyte,” which is a type of white blood cell that is responsible for recognizing and fighting foreign organisms like bacteria that have entered the body. It alerts the rest of the immune system and helps the body mount an immune response.

A Langerhans cell is a type of histiocyte that lives in the skin. Histiocytosis means that there are too many of these histiocyte cells and they do not function normally.

Langerhans cell histiocytosis was previously known as histiocytosis X.

What causes LCH?

LCH is caused by a mutation that happens in white blood cells, causing them to grow and divide when they shouldn’t and this leads to the development of a growth or tumor. The most commonly mutated gene happens in about two of every three cases of LCH and is called BRAF, though other related genes can cause it as well.

LCH isn’t contagious, so you can’t catch it from someone else, and it isn’t hereditary. The mutation in the white blood cell usually happens by chance. There was a debate for a long time about whether LCH was a problem with the immune system or a neoplastic problem like cancer. The discovery of mutations that cause LCH put it more in the neoplastic category, although LCH does not act like a cancer or malignancy in most cases.

Who gets LCH?

LCH can happen in anyone but most often happens in infants and young children. People who smoke are more likely to develop lung LCH.