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Histiocytosis
Classification & external resources

ICD-10	C96.1, D76.0
ICD-9	202.3, 277.89
eMedicine	ped/1997
MeSH	D015614

Though histiocytosis can refer to any of several specific diseases, the term is generally used to refer to a rare blood disease that is caused by an excess of white blood cells called histiocytes.

The vast majority of people diagnosed with histiocytosis are children under the age of 10,^[1] but it is also found in adults of all ages.

It is estimated that histiocytosis affects 1 in 200,000 children born each year in the United States.

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

Contents 1 Presentation 2 Classification, and relationships to other conditions 3 Common treatments 4 Organizations 5 References 6 External links

The histiocytes cluster together and can attack the skin, bones, lung, liver, spleen, gums, ears, eyes, and/or the central nervous system.

The disease can range from limited involvement that spontaneously regresses to progressive multiorgan involvement that can be chronic and debilitating.

In some cases, the disease can be life-threatening.

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

In some ways, histiocytosis is similar to cancer^[2] and has historically been treated by oncologists with chemotherapy and radiation. Unlike cancer, histiocytosis sometimes goes into remission without treatment.

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.^[3][4]. However, the classifications in ICD10 and MeSH are slightly different, as shown below:

Name	WHO	ICD10	MeSH
Langerhans cell histiocytosis (LCH)	I	D76.0	Langerhans-cell histiocytosis
Juvenile xanthogranuloma (JXG)	II	D76.3	non-Langerhans-cell histiocytosis
Hemophagocytic lymphohistiocytosis (HLH)	II	D76.1	non-Langerhans-cell histiocytosis
Niemann-Pick disease	-	E75.2	non-Langerhans-cell histiocytosis
Sea-blue histiocyte syndrome	-	-	non-Langerhans-cell histiocytosis
Acute monocytic leukemia	III	C93.0	malignant histiocytic disorders
Malignant histiocytosis	III	C96.1	malignant histiocytic disorders
Erdheim-Chester disease	-	C96.1	malignant histiocytic disorders

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

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

This illness is so rare, there is little research into its cause and treatment, and it is often referred to as an orphan disease, meaning it strikes too few people to generate government-supported research and that no particular medical specialisms "own" the disease and no large organisations are providing support.

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]).

1. ^ http://www.ucsfhealth.org/childrens/medical_services/cancer/histio/conditions/histio/signs.html
2. ^ http://www.hopkinskimmelcancercenter.org/scout/types/histiocytosis.cfm
3. ^ 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. 
4. ^ http://www.emedicine.com/ped/topic1997.htm#targetH

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