Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (24 page)

   Vasculitic phase: systemic vasculitis that can be life threatening and is often associated with vascular and extravascular granulomatosis.

   See Table
2-1
.

TABLE 2–1. The American College of Rheumatology 1990 Criteria for the Classification of Vasculitis

Adapted from the website of the American College of Rheumatology (
www.rheumatology.org
).

   Who Should Be Suspected?

   Candidates are patients with asthma that is poorly controlled and a necrotizing eosinophilic vasculitis. In addition to pulmonary and sinus involvement, organs commonly affected by EGPA include the skin, kidneys, peripheral nervous system, gastrointestinal tract, and cardiovascular system. Cardiac involvement accounts for approximately one half of deaths attributable to EGPA.

   EGPA frequently occurs in patients between 40 and 60 years of age.

   Laboratory Findings

Diagnosis relies on a combination of tissue biopsy (eosinophilic infiltrates, necrosis, and eosinophilic giant cell vasculitis) and laboratory testing.

   Leukocytosis with peripheral blood eosinophilia (>1,500 cells/μL; usually in the 5,000–9,000 range) is found in approximately 90% of patients. Eosinophilia may be missed in some cases due to spontaneous fluctuations or corticosteroid therapy preceding the diagnosis.

   Circulating ANCAs are present in 40–60% of EGPA cases. The majority of ANCA-positive patients have antibodies against myeloperoxidase (MPO), with a perinuclear staining pattern (p-ANCA).

   Elevated serum IgE during the vasculitic phase.

   Hypergammaglobulinemia and markedly elevated ESR and CRP.

   Complement components (C3, C4, CH50) may be normal or elevated.

   Normochromic, normocytic anemia.