Cogan syndrome--pathogenesis, clinical variants and treatment approaches

Non-syphilitic keratitis, coexisting with vestiboloauditory symptoms namely hearing loss and dizziness was first reported by Morgan and Baumgartner back in 1934. It was then ten years later when D.G. Cogan, an ophthalmologist (1908-1993) described 4 patients having the same symptoms but in addition, attacks of vertigo, tinnitus, hearing loss and ocular symptoms. This was published in Archives of Ophthalmology in 1945 and later named Cogan's syndrome (CS). Almost 20years later on, bilateral recurrent episcleritis associated with vestiboloauditory symptoms were defined to be the atypical form of CS occurring in association with rheumatoid arthritis (RA). During the coming two decades the division of CS into typical (classical) and atypical variants, based mainly on the clinical presentation of this syndrome was accepted. Typical CS manifests primarily with interstitial keratitis and hearing loss, whereas atypical CS is usually presented with scleritis, chroiditis and more frequently with systemic inflammation. Approximately, 70% of these patients have systemic manifestations, of which vasculitis is considered the pathogenic mechanism and therefore carries a less favorable prognosis than typical CS. Since then, CS was considered by many to be autoimmune or immune mediated in origin, supported mainly by the beneficial response to corticosteroids. It was only later, using well developed assays such as western blotting and immunofluorescence (IF) when antibodies to inner ear antigens, anti neutrophil cytoplasmic antibodies (ANCA) and anti-endothelial antibodies were found and described to be associated with CS.