In situ labelling of fragmented DNA in cutaneous necrotizing vasculitis

Apoptosis is a biochemically and morphologically gene-regulated distinctive form of cell death playing a pivotal role in tissue homeostatis, viral infections and clearance of damaged cells. The process is initiated by a cascade of intercellular and intracellular signals through an intrinsic cell suicide program resulting in early DNA fragmentation characterized by nuclear and cytoplasmic condensation. Recently some authors have reported apoptosis to occur in several inflammatory skin diseases, such as lichenoid reactions and cutaneous lymphomas. The aim of our study is to investigate the apoptotic phenomenon in two different forms of cutaneous necrotizing vasculitis (CNV) affecting the postcapillary venules such as leukocytoclastic and lymphocytic cutaneous vasculitis. For this purpose, the in situ nick end labelling of fragmented DNA technique has been performed on lesional skin biopsies from patients with acute phase of the disease. In both leukocytoclastic and lymphocytic forms apoptotic bodies were detected, evidencing two different characteristic patterns of distribution, probably related to the different nature of cellular inflammatory infiltrate. Our results seem to account for the involvement of apoptotic phenomena in cutaneous vasculitis; furthermore, the evaluation of in situ DNA fragmentation could be a useful tool to discriminate different forms of the disease.