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In medicine, histiocytosis is an excessive number of histiocytes[1] (tissue macrophages), and the term is also often used to refer to a group of rare diseases which share this sign as a characteristic. Occasionally and confusingly, the term "histiocytosis" 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, although the disease can afflict adults. The disease usually occurs from birth to age 15.[3]

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


Types of LCH have also been known as "eosinophilic granuloma", "Hand-Schuller-Christian disease", "Letterer-Siwe disease", and "histiocytosis X"[citation needed]

Alternatively, histiocytoses may be divided into the following groups:[4]: 714–724 

Lymphohistiocytosis is "a widespread infiltrate of non-malignant lymphocytes and macrophages, involving principally the liver, spleen and central nervous system and associated with a severe lymphoid atrophy."[5]


Sinus histiocytosis, a common feature in lymph node biopsies, is characterized by dilated sinuses containing variable numbers of histiocytes.[6]


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.[7][8] However, the classifications in ICD10 and MeSH are slightly different, as shown below:

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 histiocytosis 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



Patients and families can gain support and educational materials from the Histiocytosis Association[citation needed]

The Histiocyte Society, a nonprofit organization, is a group of more than 200 physicians and scientists from around the world committed to improving the lives of patients with histiocytic disorders by conducting clinical and laboratory research into the causes and treatment of this disease. The Society has instituted several clinical trials and treatment plans.[9][10]

The NACHO is a group of institutions that collaborate on scientific and clinical research for histiocytic diseases. Established in 2014 by 12 institutions, it was funded through a consortium grant from the St. Baldrick's Foundation.[citation needed]


  1. ^ Histiocytosis Archived 2016-10-09 at the Wayback Machine at eMedicine Dictionary
  2. ^ Disease information at the Histiocytosis Association of America
  3. ^ "Histiocytosis - Signs and Symptoms". Archived from the original on 2007-09-28. Retrieved 2007-05-07.
  4. ^ James, William D.; Berger, Timothy G.; et al. (2006). Andrews' Diseases of the Skin: clinical Dermatology. Saunders Elsevier. ISBN 0-7216-2921-0.
  5. ^ Goldberg, J; Nezelof, C (1986), "Lymphohistiocytosis: a multi-factorial syndrome of macrophagic activation clinico-pathological study of 38 cases", Hematol Oncol, 4 (4): 275–289, doi:10.1002/hon.2900040405, PMID 3557322, S2CID 30623642.
  6. ^ Egan, Caoimhe; Jaffe, Elaine S. (2018). "Non-neoplastic histiocytic and dendritic cell disorders in lymph nodes". Seminars in Diagnostic Pathology. 35 (1): 20–33. doi:10.1053/j.semdp.2017.11.002. ISSN 0740-2570. PMC 5803315. PMID 29150219.
  7. ^ 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.
  8. ^ Histiocytosis at eMedicine
  9. ^ Tebbi, Cameron K. (16 September 2020). Kanwar, Vikramjit S (ed.). "What is the Histiocyte Society classification of histiocytosis syndromes?". Medscape. Retrieved 4 December 2020.
  10. ^ Chang, Karen L.; Snyder, David S. (2007). "17. Langerhans Cell Histiocytosis". In Stephen M. Ansell (ed.). Rare Hematological Malignancies. Springer Science & Business Media. p. 383. ISBN 978-0-387-73743-0.

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