Title: Malignant histiocytosis

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| name            = Malignant histiocytosis
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| synonyms        =   Histiocytic medullary reticulosis&lt;ref name=&quot;Andrews&quot;&gt;{{cite book |author1=James, William D. |author2=Berger, Timothy G. |title=Andrews' Diseases of the Skin: clinical Dermatology |publisher=Saunders Elsevier |year=2006 |isbn=0-7216-2921-0 |display-authors=etal}}&lt;/ref&gt;{{rp|744}}
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'''Malignant histiocytosis'''  is a rare [[hereditary disease]] found in the [[Bernese Mountain Dog]] and humans, characterized by [[histiocyte|histiocytic]] infiltration of the lungs and [[lymph node]]s.  The [[liver]], [[spleen]], and [[central nervous system]] can also be affected.  Histiocytes are a component of the [[immune system]] that proliferate abnormally in this disease.  In addition to its importance in veterinary medicine, the condition is also important in human pathology.&lt;ref&gt;{{Cite web|url=https://dermnetnz.org/topics/malignant-histiocytoses|title=Malignant histiocytoses &amp;#124; DermNet NZ|website=dermnetnz.org}}&lt;/ref&gt;

==Histiocytic disorders==
A histiocyte is a differentiated tissue cell that has its origin in the [[bone marrow]].  The source for histiocytes is the [[monocyte]]/[[macrophage]] line.  Monocytes (found in the blood) and macrophages (found in tissue) are responsible for [[phagocytosis]] (ingestion) of foreign material in the body.  [[Langerhans cell]]s are [[dendritic cell]]s found in the skin and function by internalizing [[antigen]]s (foreign particles) and presenting them to [[T cell]]s.  They arise from monocytes.&lt;ref&gt;{{cite journal |vauthors=Ginhoux F, Tacke F, Angeli V, Bogunovic M, Loubeau M, Dai XM, Stanley ER, Randolph GJ, Merad M |title=Langerhans cells arise from monocytes in vivo |journal=Nat. Immunol. |volume=7 |issue=3 |pages=265–73 |year=2006 |pmid=16444257 |doi=10.1038/ni1307|pmc=4727824 }}&lt;/ref&gt;  Histiocytic disorders refer to diseases that are caused by abnormal behavior of these cells.  They include the following:
* Reactive diseases of Langerhans cells (most important feature in immune histochemistry is expression of E-cadherin)
** [[Histiocytoma (dog)|Histiocytoma]]s
* Reactive histiocytosis (immunohistochemical features show that interstitial/dermal DCs are involved)
** Cutaneous [[histiocytosis]] (CH)
** Systemic histiocytosis (SH)
* Reactive diseases of macrophages
** [[Hemophagocytic syndrome]] – a condition where macrophages phagocytose [[myeloid]] and [[erythroid]] precursors (similar to [[HLH (Hemophagocytic lymphohistiocytosis)|hemophagocytic lymphohistiocytosis]] in humans)
* Histiocytic sarcoma complex (immunohistochemical features of dendritic cells, possibly interdigitating or perivascular DCs)
** Malignant histiocytosis
** Diffuse [[histiocytic sarcoma]]
** Localized histiocytic sarcoma
* Malignant diseases of macrophages
** [[Histiocytic lymphoma]]

==Breed disposition==
Up to 25 percent of Bernese Mountain Dogs may develop malignant histiocytosis in their lifetime.&lt;ref&gt;E Cadieu, B Hedan, G Parker H, Gr Rutteman, A Baffoe-Bonnie, et al.. Genetics of Malignant Histiocytosis in the Bernese Mountain Dog. 3rd International Conference on Advances in Feline and Canine Genomics, 2006, UC Davis, United States. pp.Inconnu. ⟨hal-02815226⟩&lt;/ref&gt;{{better source|reason=Conference paper not peer review journal|date=July 2020}} Other breeds with a possible genetic tendency toward malignant histiocytosis include [[Rottweiler]]s, [[Flat-Coated Retriever]]s, and [[Golden Retriever]]s.&lt;ref name=Ettinger_1995&gt;{{cite book|author1=Ettinger, Stephen J. |author2=Feldman, Edward C. |title=Textbook of Veterinary Internal Medicine|edition=4th|publisher=W.B. Saunders Company|year=1995|isbn=0-7216-6795-3}}&lt;/ref&gt;{{page number|date=July 2020}}

==Signs and symptoms==
The disease in the lungs is characterized by enlargement of the [[tracheobronchial lymph nodes]] and infiltration of the lungs, sometimes leading to lung lobe consolidation and [[pleural effusion]].&lt;ref&gt;{{cite web|author=Kessler, Martin|year=2006|title=Radiographic diagnosis of primary and metastatic lung tumors|work=Proceedings of the North American Veterinary Conference|url=http://www.ivis.org/proceedings/navc/2006/SAE/275.pdf?LA=1|access-date=2007-01-28|url-status=dead|archive-url=https://web.archive.org/web/20070929105002/http://www.ivis.org/proceedings/navc/2006/SAE/275.pdf?LA=1|archive-date=2007-09-29}}&lt;/ref&gt;  Signs and symptoms include [[cough]], loss of appetite, weight loss, anemia, and difficulty breathing.&lt;ref&gt;{{cite web | last = Affolter | first = Verena K. | title = Histiocytic Proliferative Diseases in Dogs and Cats | work = Proceedings of the 29th World Congress of the World Small Animal Veterinary Association | year = 2004 | url = http://www.vin.com/proceedings/Proceedings.plx?CID=WSAVA2004&amp;PID=8600&amp;O=Generic | access-date = 2007-01-28 }}&lt;/ref&gt;  [[Seizure]]s and rear limb weakness can be seen.  Invasion of the bone marrow can cause [[pancytopenia]].&lt;ref&gt;{{cite journal | last = Kearns | first = Shawn Ann |author2=Ewing, Patty | title = Causes of canine and feline pancytopenia | journal = Compendium on Continuing Education for the Practicing Veterinarian | volume = 28 | issue = 2 | pages = 122–133 | publisher = Veterinary Learning Systems | date = Feb 2006 }}&lt;/ref&gt;  Diagnosis requires a [[biopsy]].

==Treatment==
Treatment with [[chemotherapy]] has been used with some success, particularly using [[lomustine]], [[prednisone]], [[doxorubicin]], and [[cyclophosphamide]].&lt;ref name=DVM&gt;{{cite journal | last = Cronin | first = Kim | title = Deciphering the histiocytic code | journal = DVM | pages = 1S–8S | publisher = Advanstar Communications | date = Dec 2006 }}&lt;/ref&gt;  Because of the rapid progression of this aggressive disease, the [[prognosis]] is very poor.&lt;ref&gt;{{cite journal |vauthors=Affolter V, Moore P |s2cid=17366063 |title=Localized and disseminated histiocytic sarcoma of dendritic cell origin in dogs |journal=Vet Pathol |volume=39 |issue=1 |pages=74–83 |year=2002 |pmid=12102221 |doi=10.1354/vp.39-1-74}}&lt;/ref&gt;

==Other histiocytic diseases in Bernese Mountain Dogs==
A similar disease is '''diffuse histiocytic sarcoma''', a term used to designate a localized histiocytic sarcoma that has spread throughout the body. Other signs and symptoms include weight loss and loss of appetite.&lt;ref name=DVM/&gt;{{better source|reason=Website, not peer reviewed journal|date=July 2020}}

==See also==
* [[Histiocytosis]]

==References==
{{Reflist}}

== External links ==

{{Medical resources
|   DiseasesDB     =
|   ICD10          = {{ICD10|C|96|1|c|81}}
|   ICD9           = {{ICD9|202.3}}
|   ICDO           = {{ICDO|9750|3}}
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|   MeshID         = D015620
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{{Histiocytosis}}

[[Category:Dog diseases]]
[[Category:Lymphoid-related cutaneous conditions]]
[[Category:Histiocytosis]]