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Nomenclature and Definitions

Pulmonary vasculitis is usually a manifestation of a systemic disorder leading to inflammation of vessels of different sizes by a variety of immunological mechanisms. Vasculitis can be categorized into primary vasculitis and secondary vasculitis. The primary systemic vasculitides are a heterogeneous group of syndromes of unknown etiology, which share a clinical response to immunosuppressive therapy (Table 74-1). Their wide spectrum of frequently overlapping clinical manifestations is defined by the size and location of the affected vessels as well as the nature of the inflammatory infiltrate. Secondary vasculitis may represent significant management problems in the context of a well-defined underlying disorder, such as diffuse alveolar hemorrhage caused by systemic lupus erythematosus (SLE). Alternatively, secondary vasculitis may be an incidental histopathological finding, for instance, in the context of an infection or necrotizing sarcoid granulomatosis.

Table 74-1Chapel Hill Consensus Nomenclature of the Primary Systemic Vasculitides

Classification schemes and definitions of the various forms of vasculitis have evolved over the past decades. Historically, the classification of the vasculitis has been based on the size of the most prominently affected vessels. The primary purpose of classification and nomenclature is to standardize communication between clinicians and investigators and to facilitate more uniform treatment approaches. Ideally, they reflect the current understanding of pathogenesis. The first international consensus conference on the nomenclature of systemic vasculitides held in 1992 in Chapel Hill aimed to reconcile definitions and classification schemes used by European and American investigators. The resulting nomenclature and definitions were based mainly on histopathological criteria, particularly the size of the vessels involved, but allowed for radiographic and clinical surrogates to fulfill the definitions. These definitions, nomenclature, and classification found wide acceptance. The terminology was recently revised and updated at the second 2012 Chapel Hill International Consensus Conference so that it reflects novel insights into the pathogenesis of various vasculitides while avoiding the use of eponyms as much as possible.1 In this chapter, the specific definition of each form of vasculitis is discussed in detail as part of the description of the clinical manifestations and differential diagnosis of each entity.

The 2012 Chapel Hill nomenclature is clinically very useful to pulmonologists as it reflects the clinical and histopathological pulmonary features and facilitates the therapeutic approach to individual patients. The three ...

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