Defects of steroidogenesis.

We report a 62-year-old man with mild fever, headache and acute visual loss in his right eye due to anterior ischaemic optic neuropathy (AION), followed a few days later by pain in the legs and left arm associated with numbness and weakness. Giant cell arteritis complicated by AION was suspected at the beginning and high-dose oral glucocorticoids were started. However, on the basis of the past medical history of nasal polyposis, asthma, and hypereosynophilia as well as of further investigations (biopsy of the nasal mucosa showing granulomatous inflammation with a rich eosinophilic infiltrate, electromyography demonstrating, mononeuritis multiplex and positive p-ANCA), eosinophilic granulomatosis with polyangiitis (EGPA), previously known as Churg-Strauss syndrome, was diagnosed. Because visual acuity in the right eye deteriorated despite glucocorticoid therapy, pulse intravenous cyclophosphamide was started, subsequently replaced by oral azathioprine, while prednisone was slowly tapered. This treatment led to gradual improvement of the neurological symptoms, whereas the right visual impairment remained unchanged. EGPA-related AION is an uncommon lesion that is probably due to vasculitic involvement of posterior ciliary and/or chorioretinal arteries. The prognosis of established AION is poor for the affected eye, even when glucocorticoid treatment is started immediately. However, early recognition of AION and prompt aggressive treatment with high-dose glucocorticoids plus cyclophosphamide can prevent visual loss in the unaffected eye.