ABSTRACT
Wegener’s granulomatosis (WG) is a multisystem autoimmune disease charac-
terized by necrotizing granulomatous inflammation predominantly affecting the
respiratory tract and a necrotizing small vessel vasculitis centered on capillaries,
arterioles, and venules (1,2). Specific disease manifestations depend on the
predominant type of histopathologic lesions and their location. The disease
typically runs a relapsing and remitting course, with one or more relapses in
approximately 50% of patients (1,3). The vasculitic disease manifestations of
WG are shared with microscopic polyangiitis (MPA), but the presence of
necrotizing granulomatous inflammation sets WG apart from MPA. WG and
MPA also share the frequent presence of antineutrophil cyoplasmic autoanti-
bodies (ANCAs) in the serum of patients (4). In WG, they are usually directed
against the neutrophil granule protease, proteinase 3 (PR3), and cause a cyto-
plasmic immunofluorescence pattern (c-ANCA) on ethanol-fixed neutrophils
(4). ANCAs occurring in MPA are more frequently directed against the
neutrophil enzyme myeloperoxidase (MPO) and cause a perinuclear immuno-
fluorescence pattern (p-ANCA) on ethanol-fixed neutrophils. Given the overlap
of the histopathologic features and organ manifestations between WG and MPA,
the separation of the syndromes is sometimes difficult. Similarly, the ANCA
subtype does not allow a clear separation of the two. Consequently, these two
ANCA-associated vasculitides (AAV) are often viewed as parts of a disease
spectrum that shares pathogenic mechanisms and calls for the application of the
same treatment strategies. Treatment strategies for WG and other AAV (discussed
in detail later) developed in the 1970s and 1980s dramatically improved the
prognosis of what previously was a fatal disease (3,5,6).
