Langerhans cell histiocytosis (LCH)
Adult histiocyte disorders are rare diseases. The most common of these is Langerhans cell histiocytosis (LCH), which affects only a few hundred patients every year in the United States.
LCH results from the body's overproduction of immature histiocytes, which are a type of white blood immune cell. While Langerhans cells are found in normal, healthy persons, an over-production and build-up of these cells can lead to organ damage. As we have learned much more about the biology of LCH, we now know that the disease does not actually originate from Langerhans cell, but from a more immature cell called a myeloid dendritic cell.
Langerhans cells reside mostly in the skin, although they are also present in the lung, bone marrow, lymph nodes and other areas.
The organs most commonly affected by LCH are:
- Bone: 77 percent
- Skin: 39 percent
- Lymph nodes: 19 percent
- Liver: 16 percent
- Spleen: 13 percent
- Oral mucosa: 13 percent
- Lung: 10 percent
- Central nervous system: 6 percent
LCH is not known to be an inherited genetic disease. However, we are collaborating with researchers at Texas Children's Hospital to prove or disprove whether this is the case. The risk of LCH in the lung is known to be increased in smokers.
In the past, LCH has also been known as eosinophilic granuloma, histiocytosis X, and Letterer-Siwe disease. All of these entities are now included under LCH.
Signs and symptoms
The signs and symptoms of LCH depend on the organ affected:
- Bone involvement can cause pain, often in a very specific area where the disease is eroding the bone. The most commonly affected bones are the skull, jaw (particularly the lower jaw), ribs, pelvis, and vertebrae, but any bone can be affected.
- Skin involvement often presents as single or multiple small red lumps, but the skin rash can also be flat, itchy, and flaky much like eczema or psoriasis. The scalp, ear canals, and vulva are common sites of skin involvement. Some patients develop mouth sores similar to canker sores, but often larger and flatter.
- Lymph node involvement is usually found on radiology scans or by feeling painless, rubbery lumps in the neck, under the arms, or in the groin.
- Liver involvement usually does not cause symptoms, but is detected by blood work or scans.
- Spleen involvement can be detected on physical exam or by a decrease in blood counts.
- Lung involvement is particularly common in smokers and can cause a chronic cough or shortness of breath.
- Central nervous system (CNS) involvement most commonly affects the pituitary gland, a master gland that controls function of the thyroid, adrenal, and reproductive glands. A common manifestation of CNS is diabetes insipidus. This is different from diabetes mellitus ("sugar diabetes") and has nothing to do with blood sugar. Instead, the body is unable to make the hormone that allows the kidneys to reabsorb water. As a result, patients can have extreme thirst or urination.
Rarely, patients with CNS involvement can develop a condition called a neurodegenerative syndrome, which causes memory loss and problems with speech and balance.
LCH is often less aggressive in adults than in children. Liver, spleen, and lymph node involvement are relatively uncommon in adults. LCH is a strange disease, however, and can remain quiet for years or decades. Some patients are diagnosed and treated as children, and then have a recurrence well into adulthood.
Other histiocyte disorders
Erdheim-Chester disease (ECD)
Erdheim-Chester disease (ECD) is an extremely rare form of non-Langerhans cell histiocytosis, with only a few hundred cases reported in the literature. There are no identified risk factors, and ECD is not known to be an inherited disease.
Common sites of involvement include the retroperitoneum (back of the abdomen), often with tissue growing around the kidneys. The disease classically causes symmetrical involvement of the long bones (femur and humerus) but can also affect the heart, aorta, liver, nervous system, skin, lungs, tissue near the eye, and other organs.
Depending on the organ affected, the signs and symptoms are similar to those for Langerhans cell histiocytosis. Because ECD can affect critical organs such as the heart, brain, and kidneys, monitoring with a cardiologist, neurologist, and/or kidney specialist with knowledge of the disease is very important and is a focus of our collaborative effort.
Histiocytic sarcoma (HS)
Histiocytic sarcoma (HS) is also an extremely rare form of non-Langerhans cell histiocytosis. Despite its name, histiocytic sarcoma is actually a disease of blood-derived cells, whereas true sarcomas are cancers of bone or connective tissue. The misnomer arose from the fact that the cells of histiocytic sarcoma are spindle-shaped, much like sarcoma cells.
There are no known risk factors for HS, but the disease can occur in the context of other cancers, including leukemia, lymphoma and germ cell cancers. In some cases, it is possible to show that the HS and the other cancer originated from the same primitive cell.
Histiocytic sarcoma often affects the lymph nodes, which can lead to painful lumps in the neck, under the arms, or in the groin, or abdominal pain from enlarged lymph nodes in the abdomen. Patients may have abnormal blood counts from involvement of the bone marrow with HS, or from a leukemia occurring at the same time as HS.
Rosai-Dorfman disease (RDD)
Rosai-Dorfman disease (RDD), which is most commonly seen in children, but also occurs in adults. RDD usually causes enlargement of the neck lymph nodes that resolves spontaneously. However, sometimes RDD does not resolve on its own and does require treatment. RDD can affect the bone, skin, nervous system and other organs. Also, RDD can occur with other blood-related diseases, including Hodgkin's lymphoma, or with rheumatologic diseases, such as lupus and rheumatoid arthritis, making a careful and thorough assessment critical.
Juvenile xanthogranuloma (JXG)
Juvenile xanthogranuloma (JXG), which can mimic ECD, but is often treated differently. JXG usually occurs in children but can occur along with adult-onset asthma.
Are histiocyte disorders cancers?
Experts continue to debate whether or not ECD and LCH are inflammatory disorders or blood-related cancers. Recent scientific advances — including the identification of mutations specific to these diseases — have shifted opinion towards defining ECD and LCH as cancers. HS is widely considered a blood-related cancer.