Relevance of biopsies for the diagnostics of infectious skin diseases

Abstract

Pathogen-related skin infections are acommon problem in the dermatological practice. Apart from culturing and serological detection methods, askin biopsy is apossible diagnostic procedure, especially when the clinical picture is unspecific and other non-infectious skin diseases are considered as possible differential diagnoses. Some organisms can already be detected by routine staining methods (hematoxylin & eosin, e. g., yeasts, Leishmania), for others numerous histochemical and immunohistochemical stains are available, e. g. periodic acid-Schiff reaction (PAS) and Grocott for hyphae and spores, Ziehl-Neelson and Fite-Faraco for Mycobacteria or specific antibodies for Treponema pallidum or herpesviruses. In other instances, an infectious disease may not be diagnosed with certainty in ahistological section but the pattern of inflammatory infiltrates is highly suggestive of an infectious cause. Based on such reaction patterns, the dermatopathologist can advise the clinician to perform cultures or serological investigations or additional molecular biological techniques can be applied to the biopsy specimen in order to identify the pathogens. This article presents skin infections with their histopathological features and highlights diseases that can be diagnosed with certainty in abiopsy and those in which abiopsy is helpful to exclude differential diagnoses or to perform molecular diagnostics on the specimen.