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Malignant histiocytosis
Malignant histiocytosis
Other names	Histiocytic medullary reticulosis
Specialty	Oncology, angiology

Malignant histiocytosis is a rare hereditary disease found in the Bernese Mountain Dog and humans, characterized by histiocytic infiltration of the lungs and lymph nodes. 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.^[2]

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 cells are dendritic cells found in the skin and function by internalizing antigens (foreign particles) and presenting them to T cells. They arise from monocytes.^[3] 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)
- Histiocytomas
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 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.^[4]^{[better source needed]} Other breeds with a possible genetic tendency toward malignant histiocytosis include Rottweilers, Flat-Coated Retrievers, and Golden Retrievers.^[5]^{[page needed]}

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.^[6] Signs and symptoms include cough, loss of appetite, weight loss, anemia, and difficulty breathing.^[7] Seizures and rear limb weakness can be seen. Invasion of the bone marrow can cause pancytopenia.^[8] Diagnosis requires a biopsy.

Treatment

Treatment with chemotherapy has been used with some success, particularly using lomustine, prednisone, doxorubicin, and cyclophosphamide.^[9] Because of the rapid progression of this aggressive disease, the prognosis is very poor.^[10]

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.^[9]^{[better source needed]}

References

^ James, William D.; Berger, Timothy G.; et al. (2006). Andrews' Diseases of the Skin: clinical Dermatology. Saunders Elsevier. ISBN 0-7216-2921-0.
^ "Malignant histiocytoses | DermNet NZ". dermnetnz.org.
^ Ginhoux F, Tacke F, Angeli V, Bogunovic M, Loubeau M, Dai XM, Stanley ER, Randolph GJ, Merad M (2006). "Langerhans cells arise from monocytes in vivo". Nat. Immunol. 7 (3): 265–73. doi:10.1038/ni1307. PMC 4727824. PMID 16444257.
^ 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⟩
^ Ettinger, Stephen J.; Feldman, Edward C. (1995). Textbook of Veterinary Internal Medicine (4th ed.). W.B. Saunders Company. ISBN 0-7216-6795-3.
^ Kessler, Martin (2006). "Radiographic diagnosis of primary and metastatic lung tumors" (PDF). Proceedings of the North American Veterinary Conference. Archived from the original (PDF) on 2007-09-29. Retrieved 2007-01-28.
^ Affolter, Verena K. (2004). "Histiocytic Proliferative Diseases in Dogs and Cats". Proceedings of the 29th World Congress of the World Small Animal Veterinary Association. Retrieved 2007-01-28.
^ Kearns, Shawn Ann; Ewing, Patty (Feb 2006). "Causes of canine and feline pancytopenia". Compendium on Continuing Education for the Practicing Veterinarian. 28 (2). Veterinary Learning Systems: 122–133.
^ ^a ^b Cronin, Kim (Dec 2006). "Deciphering the histiocytic code". DVM. Advanstar Communications: 1S–8S.
^ Affolter V, Moore P (2002). "Localized and disseminated histiocytic sarcoma of dendritic cell origin in dogs". Vet Pathol. 39 (1): 74–83. doi:10.1354/vp.39-1-74. PMID 12102221. S2CID 17366063.