Page 155 - The Vasculitides, Volume 1: General Considerations and Systemic Vasculitis

Nomenclature and Pathologic Features of Vasculitides 131

AAV are further categorized as MPA, GPA and EGPA [1]. Thus, when adequate
information is available, an optimum AAV diagnosis based on CHCC 2012 includes both the
ANCA serotype and the clinicopathologic phenotype, such as MPO-ANCA MPA, PR3-
ANCA MPA, MPO-ANCA GPA, PR3-ANCA GPA, ANCA-negative GPA, and MPO-
ANCA-EGPA. In a clinical setting, the serotype alone predicts some disease characteristics
(Figure 6) and outcomes as for example the frequency of recurrence after induction of
remission; while the clinicopathologic variant alone also predicts some disease characteristics
and outcomes. However, the two together give a more complete picture about the patient and
expected treatment [14]. Thus, from a practical perspective, the available information may
require that a more generic diagnosis be made initially, as for example MPO-ANCA AAV,
and then refined after more thorough evaluation or as clinical manifestations evolve such as
the emergence of compelling evidence for GPA rather than MPA.

MPA is defined as necrotizing vasculitis, with few or no immune deposits, predominantly
affecting small vessels such as capillaries, venules, and arterioles [1].

Figure 6. Frequency of PR3- and MPO-ANCA specificity correlated with clinical manifestations of
AAV disease. Organ groupings are not mutually exclusive.

Abbreviations: No Lung and No ENT (ear, nose and throat involvement): Vasculitis in any organ
except the lungs and the ENT system; Lung no ENT: Vasculitis localized in the lungs but not in
the ENT system; Lung: Vasculitis localized in the lungs without indicative markers such as
nodules or cavities, or histological proof such as granulomas indicative of granulomatous
inflammation; Plus Gastrointestinal (GI involvement): Vasculitis localized at any organ plus
involvement of the gastrointestinal tract; Plus Skin: Vasculitis localized at any organ plus dermal
involvement; Plus Nerves: Vasculitis localized at any organ plus involvement of the nerves; Any
Lung: Any type of pulmonary vasculitis such as pulmonary hemorrhage, infiltrates, nodules,
cavities, granulomas, or respiratory arrest; ENT, no Lung: Vasculitis localized to the ENT system
but not in the lungs; Any ENT: Any type of vasculitic manifestation of the ENT system; Lung with
nodules: Vasculitis localized at the lungs with radiographic proof of nodules; Lung plus ENT:
Any type of pulmonary vasculitis plus any type of vasculitic manifestation of the ENT system.
Reproduced from [14] with permission.

Necrotizing arteritis involving small and medium arteries may be present (Figure 4A).
Necrotizing glomerulonephritis is very common (Figure 4C). Pulmonary capillaritis often
occurs (Figure 4D). Granulomatous inflammation is absent.

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