Churg-Strauss syndrome.

A 51-year-old Caucasian man was hospitalized because of myalgia and fever. He had been suffering from chronic rhinitis since the age of 18 years and from asthma since the age of 45 years. Three months before hospitalization, he had received an influenza vaccine. On admission, he also complained of fatigue and paresthesias involving the lower limbs, and reported the recent onset of palpable purpura at both legs (Figure 1a). Laboratory tests are summarized in Table 1. The patient’s HLA-DRB1 genotype was positive for *04–*07 alleles, both belonging to the HLA-DRB4 gene. Chest computed tomography (CT) scan was normal, whereas head CT showed diffuse sinusitis (Figures 1c and d). Electroneurography disclosed sensorimotor polyneuropathy with signs of axonal damage affecting the right peroneal and left sural nerves. A biopsy of the purpuric lesions was performed, and histology showed leukocytoclastic vasculitis (Figure 1b). As an antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis was suspected and urinary abnormalities persisted, renal biopsy was performed. On light microscopy (Figure 2), the biopsy specimen included 24 glomeruli, 3 of which were obsolescent. Segmental necrosis was found in 30% of the glomeruli, whereas four showed extracapillary proliferation. The tubulointerstitium, arterioles, and venules were normal, with no eosinophilic infiltration. Immunofluorescence showed no immune deposits. Churg–Strauss syndrome (CSS) was diagnosed on the basis of histological findings showing vasculitis and the presence of asthma, eosinophilia, sinusitis, and polyneuropathy. Prednisone therapy (initial dose 1mg/kg/ day) induced rapid symptom remission, normalization of the eosinophil count, and urinary abnormalities. Prednisone was stopped 9 months later but was resumed soon after withdrawal because of relapsing asthma