Histopathological diagnostics of infections in rheumatology

The histopathological differential diagnoses of inflammatory infectious and inflammatory noninfectious diseases of the musculoskeletal system, particularly infectious and noninfectious arthritis, soft tissue inflammation and osteomyelitis in rheumatology are presented with a focus on the differential diagnostic possibilities and limitations; however, a diverse spectrum of pathogenic mechanisms underly these diseases, which can present with similar inflammatory response patterns. This wide spectrum of inflammatory pathogenesis of infectious and noninfectious diseases includes diseases such as rheumatoid arthritis, gouty arthritis, osteomyelitis and pyoderma gangrenosum, which cannot clinically be manifested thus necessitating a histopathological clarification. In terms of tissue sampling the following general principle applies: the larger the tissue sample and the more diverse the sites of tissue extraction, the more conclusive are the histopathological diagnostics. This diagnostic approach to infections, especially in a rheumatological context, is generally considered complementary and even supplementary to microbiological diagnostics. Furthermore, consideration of the virulence-resistance relationship, which can alter the inflammatory pattern, is of additional relevance. Consequently, definitive causal diagnostics are only achievable within the clinical, rheumatological, microbiological, laboratory medical and infectiological context.