We have recently described 2 histopathologic types of inflammatory vascular disease (IVD) in patients with Sjögren's syndrome (SS): neutrophilic IVD (NIVD) and mononuclear IVD (MIVD). Autoimmune MRL/Mp mice, which have many features of SS, spontaneously develop IVD which is histopathologically indistinguishable from that observed in human SS patients. Both MRL/Mp-+/+ and MRL/Mp-lpr/lpr mice develop MIVD which evolves into NIVD and results in decreased survival; the transition to NIVD is accelerated by the lpr gene. The presence of the lpr gene on other genetic backgrounds does not result in a similar acceleration of IVD and associated decreased survival. Thus, the spontaneous autosomal recessive mutation lpr appears to modulate the development of IVD in a strain of mice with an underlying propensity for vasculitis. Based on our observations on IVD in SS patients and MRL/Mp mice, we propose a new model which may enhance our understanding of the immunopathogenesis of IVD in connective tissue disease.