Rheumatoid arthritis histopathology

The definition of an overlap syndrome dictates that the criteria for diagnosis of both disorders (in the present context, of PM/DM and of some other connective tissue disorder), are fulfilled. It is not unexpected that those syndromes which overlap with PM/DM are also either known autoimmune conditions or ones in which an autoimmune basis is strongly suspected. The association of these disorders with PM/DM syndromes may not materially alter the basic histopathological featmes expected in PM/DM but some differences may be identifiable. The disorders most frequently associated with an overlap syndrome are rheumatoid arthritis, systemic lupus erythematosis, scleroderma, and mixed connective tissue disease. 

In many chronic inflammatory diseases, angiogenesis can be identified in the inflamed lesions. For example, in rheumatoid arthritis extensive neovascularization is present in the inflamed synovium where it is one of the earliest histopathological findings [36]. Since in RA synoviocytes exhibit characteristics of tumour cells, including somatic mutations in key regulatory genes such as H-ras and the p53 tumour suppressor, RA can be viewed as a multicentric tumour-like mass that invades and destroys its local environment [37]. Concurrent increased endothelial cell turnover may contribute to microvascular dysfunction and thereby facilitate persistent synovitis. 

Kremer JM, Alarcon GS, Weinblatt ME, Kaymakcian MV, Macaluso M, Cannon GW, Palmer WR, Sundy JS, St Clair EW, Alexander RW, Smith GJ, Axiotis CA. Clinical, laboratory, radiographic, and histopathologic features of methotrexate-associated lung injury m patients with rheumatoid arthritis a multicenter study with literature review. Arthritis Rheum 1997 40(10) 1829-37. 

Severe aplastic anemia has been described in a women who took leflunomide for 1 month for rheumatoid arthritis [65" ]. Peripheral blood analyses showed pancytopenia. Bone marrow cytomorphology and histopathology showed hypoplasia of hemopoietic lines without evidence of blasts or dysplasia. Allogeneic bone marrow stem cell transplantation was successfully performed. 

Lee HK, Kim DS, Yoo B, et al. Histopathologic pattern and chnical features of rheumatoid arthritis-associated interstitial lung disease. Chest 2005 127 2019-2027. 

Since the relevance of a particular model depends on the extent to which it mimics the human situation, the pathogenesis of the disease should be similar. The histopathology should resemble the human equivalent, and genetic influence should also be considered, for example the association of HLA-B27 with ankylosing spondylitis or HLA-DR with disorders such as rheumatoid arthritis. 

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