Histiocytosis

Histiocytosis
Classification and external resources
ICD-10	C96.1, D76.0
ICD-9	202.3, 277.89
eMedicine	ped/1997
MeSH	D015614

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

The histiocytes may attack skin, bone, muscles, and other important organs, including the liver, lung, spleen, and hematopoietic system. The disease is somewhat similar to cancer, and treatment often involves radiation and chemotherapy.

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.

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:

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	II	E75.2	non-Langerhans-cell histiocytosis
Sea-blue histiocyte syndrome	II	-	non-Langerhans-cell histiocytosis
Acute monocytic leukemia	III	C93.0	malignant histiocytic disorders
Malignant histiocytosis	III	C96.1	malignant histiocytic disorders
Erdheim-Chester disease	II	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 Langerhans cell histiocytosis for details).

Alternatively, histiocytoses may be divided into the following groups:^[6]:714-724

• X-type histiocytoses
• Non-X histiocytoses

Common treatments

• Chemotherapy
  • Cladribine (also known as 2CDA or Leustatin)
  • Etoposide
  • Vinblastine (Velban)

Organizations

Patients and families can gain some support by contacting patient organisations such as the Histiocytosis Association of America, which has several stable and proven treatment protocols available only for physicians,^[7] or the Histiocytosis Research Trust.

References

1. ^ Histiocytosis at eMedicine Dictionary
2. ^ Disease information at the Histiocytosis Association of America
3. ^ Histiocytosis - Signs and Symptoms
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. doi:10.1023/A:1008375931236. PMID 10643532. 
5. ^ Histiocytosis at eMedicine
6. ^ James, William D.; Berger, Timothy G.; et al. (2006). Andrews' Diseases of the Skin: clinical Dermatology. Saunders Elsevier. ISBN 0-7216-2921-0. 
7. ^ Histio.Org Physicians Information Request