Histiocytosis X has typically been thought of as a cancer-like condition. But more recently, researchers have begun to think it may be an autoimmune disorder. In this type of disorder, a person's immune cells mistakenly attack the body, rather than help the body fight infections. The extra immune cells the body makes 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, which means they are inherited.
Histiocytosis X is thought to affect roughly 1 in 200,000 people each year. It is most often seen in children ages 1 - 15, with the highest rate among children ages 5 - 10.
Pulmonary histiocytosis X is a specific type of histiocytosis X that involves swelling of the small airways and small blood vessels in the lungs. This inflammation leads to lung stiffening and damage. It is most common in 30 - 40 year old adults, usually cigarette smokers. The cause is unknown.
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, but they may have some of the same symptoms. Tumors in weight-bearing bones, such as the legs or spine, may cause the bones to fracture without an obvious reason.
Histiocytosis X affects many organs and can lead to death.
About half of those with pulmonary histiocytosis improve, while others have permanent loss of lung function over time.
In very young patients, the outlook depends on the specific histiocytosis and how severe it is. Some children can live a normal life with minimal disease involvement, while others do poorly. Young children, especially infants, are more likely to have body-wide symptoms that lead to death.
Jordan BM, Filipovich AH. Histiocytic Disorders. In: Hoffman R, Benz EJ, Silberstein, LE, et al, eds. Hematology: Basic Principles and Practice. 6th ed. Philadelphia, PA: Elsevier Churchill Livingstone; 2012:chap 50.
Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.