Cogan's syndrome. A comprehensive review.

Cogan Syndrome (CS) is a rare autoimmune systemic vasculitis affecting the inner ear and the eye with systemic manifestations affecting mainly young adults. The clinical presentation is historically classified in two subtypes. Typical CS associated interstitial keratitis with audio-vestibular symptoms with a 2-year maximum delay between these 2-organ involvements. Atypical CS subgroup associated inflammatory ocular disease in the absence of interstitial keratitis, audio-vestibular impairment, and systemic manifestations in a delay longer than 2 years between different organ manifestations. Neither diagnostic criteria nor specific biomarkers could lead to definite diagnosis. Cogan syndrome is a diagnosis of exclusion after a meticulous appropriate investigation to rule out other conditions. Disease prognosis is related to the risk of deafness and/or blindness as well as complications related to systemic vasculitis. Early recognition of this condition and early intervention can minimize disabling and irreversible damage. Treatment of CS is challenging, and the only available data comes from case reports and series. The aim of this review is to describe the clinical spectrum and outcome of CS through a summary of published case series, the differential diagnosis, and the therapeutic approaches with a special focus on the recent novel therapeutic options in the biological era.