Acute bilateral uveitis and right macular edema induced by a single infusion of zoledronic acid for the treatment of postmenopausal osteoporosis as a substitution for oral alendronate: a case report

BACKGROUND Zoledronic acid-induced uveitis (ZAIU) is rare but severe, and has been recently considered part of an acute phase reaction. Only 15 cases have been reported since 2005. Here we describe a case with macular edema, which is the first reported case observed after long-term alendronate tolerance. CASE PRESENTATION A 63-year-old Asian woman received her first intravenous zoledronic acid treatment for the management of postmenopausal osteoporosis as a more convenient substitute for oral alendronate. Twenty-four hours later, bilateral eye irritations, periorbital swelling, blurred vision, and diplopia presented. The complete blood count and transaminase levels were normal, but the erythrocytic sedimentation, C-reactive protein, and serum C4 levels were elevated. On detailed ophthalmological examination, a diagnosis of bilateral acute uveitis and macular edema in the right eye was made. The ocular symptoms were not improved until administration of topical and oral steroids. Complete resolution was achieved. There was no rechallenge of bisphosphonates, and no recurrence at 6 months follow-up. Based on an extensive review, abnormal fundus is rarely reported, especially in cases of macular edema. Rechallenge with zoledronic acid in five cases induced no additional uveitis, and changing the medication to pamidronate in another patient was also tolerated. Interestingly, our patient suffered from uveitis soon after intravenous zoledronate exposure after a two-year tolerance to oral alendronate. CONCLUSIONS This is the first report of zoledronic acid induced uveitis with macular edema after long-term alendronate tolerance. Prior oral alendronate may not entirely prevent ZAIU. Steroids are usually necessary in the treatment of ZAIU. Bisphosphonate rechallenge is not fully contraindicated, and prior steroid administration may be a more reasonable treatment choice according to the available evidence.