Page 146 - The Vasculitides, Volume 1: General Considerations and Systemic Vasculitis

122 J. Charles Jennette, Ronald J. Falk and Adil. H. M. Gasim

cytoplasmic autoantibodies; any significantly associated systemic diseases such as
rheumatoid arthritis or systemic lupus erythematosus, or associated etiologies such as
hepatitis C virus infection versus propylthiouracil exposure; as well as the organ system
distribution such as lung versus brain; accompanying extravascular lesions such as
necrotizing granulomatosis or aphthous ulcers; or other possible factors. In a given
patient, the goal of the clinician is to make a diagnosis, namely, assign a disease name
that specifies the nature of the root disease process in the patient, and correctly assigns
the particular form of vascular inflammation to the observed signs and symptoms that
comprise the clinical criteria of that disorder, while providing useful predictions about
disease outcome and appropriate treatment.

Keywords: Nomenclature, Pathology, Vasculitides, Chapel Hill Consensus Conference 2012,
ANCA

Introduction

Vasculitis is inflammation in vessel walls. The categorization and diagnosis of vasculitis
is based on the nature of the inflammatory injury in vessels, including the etiology,
pathogenesis, pathologic features and associated organ system dysfunction. The diagnosis of
vasculitis is based on signs and symptoms of the disease or diagnostic criteria that allow a
conclusion about the nature of the inflammatory injury in vessels, including the etiology,
pathogenesis and pathologic features. Criteria that lead to a diagnosis in a specific patient
may or may not involve direct microscopic visualization of inflammation or its sequela, such
as vascular scarring in a tissue sample. However, to make a diagnosis of vasculitis, a
conclusion must be reached that vasculitis with certain characteristic pathologic changes is
occurring or has occurred in the patient. Thus, the underlying basis for the diagnosis of all
patients with vasculitis is the nature of the pathologic inflammatory process that caused the
vasculitis, although this does not mean that the pathologic lesions must be directly visualized
histologically to make an actionable diagnosis.

This chapter reviews the pathology of many forms of vasculitis and presents an approach
to nomenclature, classification and diagnosis that derives from these pathologic lesions. The
2012 Chapel Hill consensus conference nomenclature system (2012 CHCC) will be
emphasized [1], since it modified and extended the 1994 CHCC nomenclature [2]. Disease
nomenclature is a system of names used to identify and categorize diseases; and as for all
words, each name has a definition.

The primary underlying defining characteristics of vasculitis in a patient are the cause
and the nature of the vascular inflammation including the type of inflammation and the
vascular distribution of inflammation. A diagnosis that refers only to cause or only to
clinical/pathologic phenotype is problematic since 1) One cause can produce more than one
pattern of injury, for example myeloperoxidase-specific anti-neutrophil cytoplasmic
autoantibodies (MPO-ANCA) causing either microscopic polyangiitis (MPA) or
granulomatosis with polyangiitis (GPA); and 2) One type of vasculitis can be induced by
multiple causes, for example MPA caused by MPO-ANCA or proteinase 3-specific ANCA
(PR3-ANCA). When possible, the definition of a vasculitis should include a reference not
only to the nature of the inflammatory vascular injury but also the likeliest cause if known.
For example, the name IgA vasculitis (IgAV) emphasizes that the vasculitis is caused by

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