Single-Organ Vasculitis

Single-organ vasculitis (SOV) is a category of vasculitis adopted at the 2012 International Chapel Hill Consensus Conference (CHCC) on the nomenclature of vasculitides that encompasses a group of diseases in which vasculitic involvement is confined to a specific organ, system, or territory. SOV may be localized in focal sites (e.g., aorta, mammary, genitourinary, and abdominal structures), or affect structures in a diffuse or multifocal fashion (e.g., isolated forms of central nervous system, cutaneous and retinal vasculitis). Focal SOV are usually incidentally found in evaluations for malignant or infectious conditions. Whereas the resection of the inflammatory lesion may resolve the inflammatory process in focal SOV, systemic immunosuppressive or immunomodulatory therapy is usually required in diffuse SOV. Because the territories targeted in systemic vasculitis may also be affected in SOV, SOV diagnosis always requires to exclude a systemic illness and also to reassure that it is not a limited expression of a systemic vasculitis. Except for some forms of aortic, gastrointestinal, or urologic SOV, which can be associated with local rupture or obstruction with severe or fatal consequences, the prognosis of focal SOV in other locations is usually favorable. In some focal SOV forms, certain clinical, laboratory, and histopathologic features may contribute in distinguishing isolated from systemic vasculitis, and subsequently, in developing diagnostic and therapeutic strategies.