A patient describes her successful treatment for Erdheim-Chester disease as a result of participating in an MSK basket trial.

Histiocytosis is a group of disorders in which there are an abnormally high number of white blood cells called histiocytes. These diseases can be difficult to diagnose.

The symptoms are common physical problems not specific to these diseases. These include pain, fever, rash, and frequent urination. Symptoms depend on where the tumors have formed as well as the organs and systems involved and their functions. Tumors in weight-bearing bones, such as the legs or spine, may cause the bones to fracture. Histiocytes can also form small tumors in the mouth and gums and on the skin.

Diagnosis may come through x-rays or other imaging methods, blood tests, or biopsies of tumors and bone marrow.

Depending on the extent of the disease, our doctors may recommend chemotherapy. Low doses of radiation therapy or surgery may be needed to treat skin or bone tumors caused by histiocytosis.

Langerhans Cell Histiocytosis

The most common form of histiocytosis is Langerhans cell histiocytosis. Research has shown that Langerhans cell histiocytosis tumors often have mutations in a gene called BRAF V600. The protein produced by this mutated gene has been shown to promote the growth of some cancers, such as melanoma and some lung cancers.

Erdheim-Chester Disease (ECD)

The mutated BRAF V600 gene also appears in another, more rare form of histiocytosis called Erdheim-Chester disease (ECD). MSK researchers are looking for other genetic changes in people with ECD. We are trying to find the type of cell in which ECD starts. That could allow us to determine the best targeted therapy for treating people with the BRAF V600 mutation. We are researching new treatment options for people with Langerhans cell histiocytosis and ECD.