This report describes a patient who presented with features typical of IRVAN in whom medical evaluation disclosed allergic fungal sinusitis. Resolution of arterial sheathing, regression of several of the aneurysmal dilatations, and decrease in lipid exudate deposition were noted over a 3-year period follow-up. Case reportA 16-year-old boy presented with a 12-month history of decreased vision in both eyes. The patient's medical history was significant for asthma, however, not on regular treatment. He had progressive nasal obstruction associated with headache, sneezing, and itching. Review of systems revealed no history of fever, weight loss, skin lesions, arthritis, or genital ulcers. On examination, visual acuity was 20/60 in the right eye, and 20/100 in the left. Intraocular pressure by applanation was 14 mmHg, bilaterally, and pupillary reactions were normal. External examination and slit-lamp biomicroscopy were normal with clear anterior chambers. There were trace vitreous cells present in both eyes. Fundus examination disclosed bilateral extensive peripapillary and macular lipid exudate deposition. Marked and extensive sheathing of retinal arterioles was present associated with periarteriolar intraretinal haemorrhages. Numerous aneurysmal dilatations were present on the optic nerve head and along the first-and second-order retinal arterioles. The optic discs showed swelling and hyperaemia. Fluorescein angiography accentuated the numerous aneurysmal dilatations on the retinal arterioles, and showed extensive leakage from aneurysmal dilatations on the optic nerve head and on the retinal arterioles, and late staining of the aneurysmal dilatations. Both optic nerve heads demonstrated leakage and stained in the later stages (Figures 1 and 2). Extensive areas of peripheral capillary nonperfusion and adjacent anomalous arteriovenous anastomosis were present in both eyes (Figure 3). The following laboratory investigations were requested: chest X-ray, complete blood count, erythrocyte sedimentation rate, routine blood chemistry, haemoglobin electrophoresis, serum protein electrophoresis, urinalysis, Venereal Disease Research Laboratory test (VDRL), fluorescent treponemal antibody absorption test, Mantoux test, antinuclear antibody, anti-double-stranded DNA antibody, antiphospholipid antibodies including anticardiolipin and lupus anticoagulant antibodies, anti-neutrophil cytoplasmic antibodies, and computed tomographic scan of the brain. A peripheral eosinophilia was present. There were no other laboratory abnormalities. Neurologic and cardiovascular examinations were normal. ENT examination revealed multiple left-sided nasal polyps. Computed tomographic scan of the IRVAN AM Abu El-Asrar et al 197