The lung in systemic vasculitis: radiological patterns and differential diagnosis.

The respiratory system may be involved in all systemic vasculitides, although with a variable frequency. The aim of our review is to describe radiographic and high-resolution CT (HRCT) findings of pulmonary vasculitides and to correlate radiological findings with pathological results. Lung disease is a common feature of antineutrophil cytoplasmic autoantibody-associated small-vessel vasculitides, including granulomatosis with polyangiitis (Wegener's), eosinophilic granulomatosis with polyangiitis (Churg-Strauss) and microscopic polyangiitis. Pulmonary involvement is less frequent in immune-complex-mediated small-vessel vasculitides, such as Behçet's disease and Goodpasture's syndrome. Pulmonary involvement associated to large-vessel (gigantocellular arteritis and Takayasu's disease) or medium-vessel (nodose polyarteritis and Kawasaki's disease) vasculitides is extremely rare. The present review describes the main clinical and radiological features of pulmonary vasculitides with major purpose to correlate HRCT findings (solitary or multiple nodules, cavitary lesions, micronodules with centrilobular or peribronchial distribution, airspace consolidations, "crazy paving", tracheobronchial involvement, interstitial disease) with pathological results paying particular attention to the description of acute life-threatening manifestations. A thorough medical history, careful clinical examination and the knowledge of radiological patterns are mandatory for a correct and early diagnosis.