Eosinophilic granulomatosis with polyangiitis

Eosinophilic granulomatosis with polyangiitis (EGPA), previously known as the Churg-Strauss syndrome (CSS), refers to a small to medium vessel necrotizing pulmonary vasculitis. It is also classified under the spectrum of eosinophilic lung disease and as a type of pulmonary angiitis and granulomatosis.

Epidemiology

The incidence typically peaks around the 3^rd to 4^th decade with an annual incidence rate of around 0.24 per 100,000 ².

Clinical presentation

Almost all patients have asthma and eosinophilia. Patients also have extrapulmonary signs and symptoms such as sinusitis, diarrhea, skin purpura, and/or arthralgias.

Diagnostic criteria

• asthma: present in almost all patients ²
• blood eosinophilia ( >10% of the total white blood cell count): present in almost all patients ^2,13
• mono/polyneuropathy
• transient pulmonary infiltrates
• paranasal sinus abnormalities: pain or radiographic abnormality
• presence of extravascular eosinophils on a biopsy specimen

Pathology

Can be histologically identical to classic polyarteritis nodosa or microscopic polyangiitis. Around 25% of patients will have renal disease ¹².

Markers

• pANCA: ~75%

Radiographic features

Plain radiograph

Chest radiographs are nonspecific but may show:

• peripheral consolidation, which may be transient/migratory
• small pleural effusions

CT

Imaging features are nonspecific:

• peripheral or random parenchymal opacification (consolidation or ground glass)
  • this tends to be the most frequent feature ¹; can be transient
  • parenchymal opacification is predominantly peripheral or random in distribution ¹
• less common features include
  • centrilobular nodules and bronchial wall thickening and/or dilatation ⁵
• cavitation is rare and if present other co-existing pathology should be considered, e.g. granulomatosis with polyangiitis, infection ⁶

MRI

Cardiac MRI

Delayed myocardial enhancement is a commonly described finding; can be intramyocardial, subepicardial or subendocardial ^9-10.

Treatment and prognosis

Corticosteroids (most commonly prednisone) are the mainstay of treatment. Patients with cardiac, renal, gastrointestinal, or CNS involvement, require additional immunosuppression (e.g. cyclosporine, azathioprine).

The condition generally has a low mortality rate compared with other systemic vasculitides ¹¹. Cardiac involvement may, however, be a significant contributor to disease-related death and may occur in up to 60% of cases ^8,13.

History and etymology

It was first described in 1951 by Jacob Churg and Lotte Strauss, American physicians based in New York ⁴.

Differential diagnosis

• for plain radiograph appearances, consider eosinophilic pneumonia