Histiocytosis is a general name for a group of syndromes that involve an abnormal increase in the number of immune cells called histiocytes.

There are three major classes of histiocytoses:

Langerhans cell histiocytosis, which is also called histiocytosis X
Malignant histiocytosis syndrome (now known as T-cell lymphoma)
Non-Langerhans cell histiocytosis (also known as hemophagocytic syndrome)
This article focuses only on Langerhans cell histiocytosis (histiocytosis X).

Causes
Histiocytosis X has typically been thought of as a cancer-like condition. More recently researchers have begun to suspect that it is actually an autoimmune phenomenon, in which immune cells mistakenly attack the body, rather than fight infections. Extra immune cells may form tumors, which can affect various parts of the body including the bones, skull, and other areas.

Some forms of the disorder are genetic.

Histiocytosis X is thought to affect roughly 1 in 200,000 people each year. It is most often seen in children ages 1 to 15. The rate peaks among children ages 5 to10.

Pulmonary histiocytosis X is a specific type of this disorder that involves swelling of the small airways (bronchioles) and small blood vessels in the lungs. It is most common in adults. The inflammation leads to lung stiffening and damage. The cause is unknown. It most often affects those ages 30 to 40, usually cigarette smokers.

Symptoms
Histiocytosis X often affects the whole body. A disease that affects the whole body is called a systemic disorder.

Symptoms can vary between children and adults, although there can be some overlap. Tumors in weight-bearing bones, such as the legs or spine, may cause the bones to fracture without apparent reason.

Symptoms in children may include:

Abdominal pain
Bone pain (possibly)
Delayed puberty
Dizziness
Ear drainage that continues long-term
Eyes that appear to stick out (protrude) more and more
Irritability
Failure to thrive
Fever
Frequent urination
Headache
Jaundice
Limping
Mental deterioration
Rash (petechiae or purpura)
Seborrheic dermatitis of the scalp
Seizures
Short stature
Swollen lymph glands
Thirst
Vomiting
Weight loss
Note: Children over 5 years old often have only bone involvement.

Symptoms in adults may include:

Bone pain
Chest pain
Cough
Fever
General discomfort, uneasiness, or ill feeling (malaise)
Increased amount of urine
Rash
Shortness of breath
Thirst and increased drinking of fluids
Weight loss
Exams and Tests
The tumors produce a "punched-out" look on a bone x-ray. Specific tests vary depending on the age of the patient.

Tests in children may also include:

Biopsy of skin to check for the presence of Langerhans cells
Bone marrow biopsy to check for the presence of Langerhans cells
Complete blood count (CBC)
X-rays of all the bones in the body (skeletal survey) to find out how many bones are affected
Tests in adults may include:

Bronchoscopy with biopsy
Chest x-ray
Pulmonary function tests
Histiocytosis X is sometimes associated with cancer. CT scans and biopsy should be done to rule out possible cancer.

Treatment
This disorder is treated with corticosteroids, which suppress immune function (including the dangerous cells). Smoking may worsen the response to treatment and should be stopped.

Children may be given other medications depending on their estimated outlook. Such medications may include:

Cyclophosphamide
Etoposide
Methotrexate
Vinblastine
Radiation therapy or surgery may also be used to treat bone lesions.

Other treatments may include:

Antibiotics to fight infections
Breathing support (with a breathing machine)
Hormone replacement therapy
Physical therapy
Special shampoos for scalp problems

Outlook (Prognosis)
Histiocytosis X affects many organs and can lead to death.

About half of those with pulmonary histiocytosis see improvement, while others eventually have permanent loss of lung function.

In very young patients, the outlook depends on the specific histiocytosis and severity of the disease. Some children can live a normal life with minimal disease involvement, while others may have a poor outcome. Young children, especially infants, are more likely to have body-wide symptoms that lead to death.

Possible Complications
Complications may include:

Diffuse interstitial pulmonary fibrosis
Spontaneous pneumothorax
Children may also develop:

Anemia caused by spreading of the tumors to the bone marrow
Diabetes insipidus
Lung problems that lead to lung failure
Problems with the pituitary gland that lead to growth failure
When to Contact a Medical Professional
Call your health care provider if you or your child have symptoms of this disorder. Go to the emergency room if shortness of breath or chest pain develop.

Prevention
Avoid smoking. Quitting smoking can improve the outcome in people with histiocytosis that affects the lungs.

There is no known prevention for the childhood forms of the disease.

Alternative Names
Histiocytosis X; Langerhans cell histiocytosis; Eosinophilic granuloma; Pulmonary histiocytosis X; Nonlipid reticuloendotheliosis; Pulmonary Langerhans cell granulomatosis; Hand-Schuller-Christian disease; Letterer-Siwe disease