Vasculitis

CHURG-STRAUSS SYNDROME

The syndrome defined by Churg and Strauss in 1951 has undergone several redefinitions but is still characterized by three histopathologic features: necrotizing vasculitis,infiltration by eosinophils, and extravascular granulomas.[189] Using only pathologic features to define the disease made it a diagnostic rarity. Thus, in 1984, Lanham and colleagues[190] suggestedthat the diagnosis be based on clinical and pathologic grounds requiring three criteria: asthma, peak eosinophil count greater than 1500 cells/mL, and systemic vasculitis involving two or more organs. In1994, the international consensus conference held in Chapel Hill, North Carolina,[174] defined the disease as an eosinophil-rich and granulomatous inflammation involving the respiratory tract andnecrotizing vasculitis involving the medium-sized vessels associated with asthma and eosinophilia. Each component of these definitions (histopathology, eosinophilia in blood and tissues, asthma) helpsdefine the disease, but none of these features individually is specific for CSS, and not every patient has all the features. Although most cases can be clearly defined, the concept of partial orincomplete CSS remains necessary.[191]

PATHOGENESIS

The cause of CSS is unknown, but its association with allergy and atopic disorders is a dominant factor. Nearly 70% of patients have a history ofallergic rhinitis, often associated with nasal polyposis; the association with asthma, usually adult onset, is part of most case definitions. Both peripheral blood and tissue eosinophilia is a majorconstituent of the syndrome, and the majority of patients tested have elevated IgE levels.[190] A link between the use of leukotriene receptor antagonists and CSS has been suggested,[192] but theepidemiologic link between this class of drugs and vasculitis is not proved.[193]

Some clinical and pathologic features of CSS are shared with the other ANCA-associated syndromes, suggesting a possible...