Cogan's syndrome: Anti-Hsp70 antibodies are a serological marker in the typical form

Background: Cogan's syndrome (CS) is a rare autoimmune vasculitis characterized by ocular inflammation and sensorineural hearing loss. CS is divided into a "typical" form with nonsyphilitic interstitial keratitis and audiovestibular symptoms, and an "atypical" form with ocular involvement affecting structures other than the cornea. Anti-Hsp70 antibodies were found at variable levels in patients presenting with various forms of autoimmune sensorineural hearing loss (ASNHL). Objectives: To assess the correlation between anti-Hsp70 antibodies and specific ASNHL subgroups. Methods: We divided 112 subjects into four groups: 14 subjects with typical CS, 24 with atypical CS, 55 with ASNHL, and 19 control subjects (healthy subjects and patients with systemic autoimmune diseases but no sensorineural hearing or audiovestibular alterations). Patients were tested for serological autoimmunity markers including anti-Hsp70. Results: Positivity of the anti-Hsp70 antibody test was highest in the typical CS group (92.9%) and lowest in the control group (5.2%). The test was positive in 52.7% of patients in the ASNHL group and 16.6% in the atypical CS group. The paired comparison analysis between groups showed that sensitivity of anti-Hsp70 in the typical CS group was significantly higher, as compared to the other three study groups. Conclusions: Anti-Hsp70 antibodies can be considered a serological marker of "typical" CS. "Atypical" CS is conceivably a sort of "melting pot" of different forms of autoimmune diseases still characterized by ocular inflammation and sensorineural hearing loss but whose antigenic characteristics need to be further defined.