In medicine, histiocytosis is an excessive number of histiocytes,^[1] that is an excessive number of tissue macrophages, and is typically used to refer to a group of rare diseases which share this as a characteristic. Occasionally and confusingly it is sometimes used to refer to individual diseases.

According to the Histiocytosis Association of America, 1 in 200,000 children in the United States are born with histiocytosis each year.^[2] HAA also states that most of the people diagnosed with histiocytosis are children under the age of 10. The University of California, San Francisco, states that the disease usually occurs from birth to age 15.^[3]

Histiocytosis (and malignant histiocytosis) are both important in veterinary as well as human pathology.

Presentation

Histiocytosis is frequently associated with diabetes insipidus, even after several years of diagnosis and successful therapy.

Classification, and relationships to other conditions

There are competing systems for classifying histiocytoses. According to the 1999 classification proposed by the World Health Organization, they can be divided into three categories.^[4][5]. However, the classifications in ICD10 and MeSH are slightly different, as shown below:

Types of LCH have also been known as "Eosinophilic Granuloma", "Hand-Schuller-Christian Disease", "Letterer-Siwe Disease", and "Histiocytosis X". (See LCH history for details).

Common treatments

• Chemotherapy
  • Cladribine or 2CDA or leustatin
  • Etoposide
  • Vinblastine or Velban

Organizations

Patients and families can gain some support by contacting patient organisations such as the Histiocytosis Association of America ([1]) or the Histiocytosis Research Trust ([2]). The Histiocytosis Association of America has several stable and proven treatment protocols available only for physicians ([3]).

References

1. ^ Stedman's Medical Dictionary. URL: http://www.emedicine.com/asp/dictionary.asp?keyword=Histiocytosis. Accessed on: May 24, 2007.
2. ^ Disease information at the Histiocytosis Association of America
3. ^ http://www.ucsfhealth.org/childrens/medical_services/cancer/histio/conditions/histio/signs.html
4. ^ Harris N, Jaffe E, Diebold J, Flandrin G, Muller-Hermelink H, Vardiman J, Lister T, Bloomfield C (1999). "The World Health Organization classification of neoplastic diseases of the hematopoietic and lymphoid tissues. Report of the Clinical Advisory Committee meeting, Airlie House, Virginia, November, 1997". Ann Oncol 10 (12): 1419-32. PMID 10643532.
5. ^ http://www.emedicine.com/ped/topic1997.htm#targetH