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).

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 age 1 to 15. The rate peaks among children age 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 aged 30 to 40, usually cigarette smokers.

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

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.

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
• Supportive care to relieve symptoms

Histiocytosis Association of America -- www.histio.org

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.

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

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.

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.

Ladisch S. Histiocytosis Syndromes of Childhood. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 507.

Raghu G. Interstitial Lung Disease. In: Goldman L, Ausiello D, eds. Cecil Textbook of Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 92.