What is Histiocytosis?
There are a few different types of Histiocytosis, this page will explain some of them as well as their symptoms.
LANGERHANS CELL HISTIOCYTOSIS (LCH)~
LCH is not strictly a cancer, but rather a cancer-like condition that may be treated with chemotherapy. In its more serious forms, LCH can behave like a cancer and is therefore usually treated by children's cancer specialists (paediatric oncologists).
Histiocytes are cells that are part of the immune system and are found in many parts of the body. There are two types of histiocytes: macrophage monocyte cells, which destroy harmful proteins, viruses and bacteria in the body, and dendritic cells, which stimulate the immune system.
Langerhans' cells are dendritic cells and are normally only found in the skin and major airways. LCH is believed to occur in 1:200,000 children, but any age group can be affected, from infancy through adulthood. In newborns and very young infants, it occurs in 1-2 per million. It is, however, believed to be under-diagnosed, since some patients may have no symptoms, while others have symptoms that are mistaken for injury or other conditions. In LCH, the Langerhans' cells are abnormal and spread via the bloodstream into many parts of the body, it can appear as a single lesion or can affect many body systems, such as skin, bone, lymph glands, liver, lung, spleen, brain, pituitary gland and bone marrow.
Treatment depends upon the individual patient and is planned after thorough testing to determine the extent of disease. In some cases, LCH may regress on its own without treatment. In others, minimal treatment such as steroids, NSAIDS (anti-inflammatory drugs), or even surgical removal will result in a positive outcome. Low-dose radiation may be helpful for some situations. In patients with more extensive disease, systemic chemotherapy is most often necessary. Several drugs and combinations have been shown in clinical trials to give excellent outcomes with minimal side effects. These drugs include steroids (prednisone), vinblastine, vincristine, etoposide (VP-16), methotrexate, cytosine arabinoside (Ara-C) and 6-MP. For patients with severe disease that progresses and is not responsive to initial treatment, chemotherapy with 2-CdA, alone or in combination with Ara-C, thalidomide or ultraviolet light (PUVA) has been used in patients with only skin disease. Steroid or other types of creams may also help limited skin disease. In very rare cases, liver, lung, or even bone-marrow transplant has been necessary for recovery.
Hemophagocytic Lymphohistiocytosis (HLH)~
life-threatening immunodeficiency. It affects people of all ages and ethnic groups. Common symptoms are fevers, enlarged spleen, low blood counts and liver abnormalities. At least half of the patients with HLH will also experience inflammation of the brain which can lead to a wide variety of neurologic problems.
The symptoms of HLH result from an overactive and poorly controlled immune response involving T lymphocytes and macrophages. This abnormally intense immune response results in prolonged and highly elevated levels of cytokines (molecules which, in minute quantities, normally regulate immune functions). This so-called "hypercytokinemia" is potentially damaging to all the major vital organs. The hallmark of hypercytokinemia is Hemophagocytosis, the process for which the disorder is named. Hemophagocytosis is an abnormal consumption of blood cells by macrophages which are turned on by the high cytokine levels, resulting in the low blood counts. The onset of FHL is usually early in life, and a permanent cure can only be achieved through a bone marrow transplant. In some ways, histiocytosis is similar to cancer, and has historically been treated by oncologists with chemotherapy and steroids to try and quiet the disease, ultimately needing a bone marrow transplant, but it is not cancer.
While some patients experience HLH symptoms which can wax and wane or respond well to steroids initially, many patients suffer from progressive illness which can lead to death if appropriate immune suppressive treatment is not begun in time. Ultimately, children and young adults who have HLH on the basis of known genetic defects will require a hematopoietic cells transplant (BMT) to cure them. Patients without a known genetic cause who experience progressive HLH or recurrent episodes are also considered for BMT. At present, with the more widespread use of Reduced Intensity Conditioning (RIC) protocols accompanied by careful selection of donor and stem cell product to be used - long term survival rates after HCT have improved from 50-70% up to 90% in experienced HCT centers.