Background Recent studies have investigated the relationship between idiopathic sensorineural hearing loss (SNHL) and autoantibodies against inner ear antigens, such as anti-Cogan peptide, anti-connexin 26, anti-DEP1/CD148 and anti-reovirus (1). Anti-Cogan peptide has an homology of sequences with Ro/SSA protein. Antibodies purified against the Cogan peptide bind specifically to human cochlea inducing an immune-mediated SHNL. Anti-Ro/SSA and SSB/La antibodies in pregnant women, cross the placenta and reach the fetal tissues inducing an immune-mediated damage of the cardiac conduction system known as neonatal lupus.
Objectives To evaluate the possible pathogenesis correlation between anti-Ro/SSA and anti-Cogan peptide antibodies.
Methods A 13-year-old boy, born from mother with Sjögren syndrome and anti-SSA/Ro antibodies, who developed a congenital heart block (CHB), treated with pacemaker implantation at birth. When 12-year-old, he developed nausea, dizziness, tinnitus, vertigo, and hearing loss. ENT evaluation revealed a moderate right SNHL. Labyrinthitis was diagnosed, and treatment with oral prednisone was started. All features disappeared in a few days, while a persistent moderate right SNHL was confirmed in the following ENT evaluations. Ten months later, the boy referred headache and dizziness, and audiometry showed a severe right SNHL, worsened when compared to the previous examination. The genotype study of connexin-26 and connexin-30 mutations was negative, so hereditary hearing loss was excluded. The study of NLRP3 gene mutations was normal, so Muckle-Wells syndrome was also ruled out. Autoantibodies against inner ear showed a positivity for anti-reovirus peptide antibodies, and a strong positivity for Cogan peptide, anti-DEP1/CD148 and anti-connexin 26 antibodies. The patient was diagnosed as having autoimmune hearing loss and was started on oral prednisone. Headache and dizziness rapidly disappeared, steroids were tapered after 3 months and hearing loss was stable.
Results We have tested the sera of 9 women with autoimmune diseases (SLE, Sjögen syndrome, and other connective tissue disorders) for antibodies against inner ear, and we have observed a cross-reaction with Cogan-peptide (in 1 case) and with anti-reovirus peptide (in 1 case). Moreover, the 60 KD SSA/Ro protein reacted with the sera of women with autoimmune disease (in 9/9), children with CHB (in 7/7), but not in patient with Cogan syndrome (0/7).
Conclusions To our knowledge, the coexistence of CHB and SNHL has not been previously reported. Interestingly, autoantibodies which are able to induce tissue damage upon binding on the sensory epithelia of the inner ear can cross-react with anti-SSA/Ro. In our patient, we have hypothesized a viral infection as possible trigger of hearing loss. More studies will be needed to determinate if purified autoantibodies, obtained from women with autoimmune diseases could cross-reactive with Cogan peptide, and if they have a role in the pathogenesis of inner ear damage.
Lunardi C, Bason C, Leandri M, Navone R, Lestani M, Millo E, Benatti U, Cilli M, Beri R, Puccetti A. Autoantibodies to inner ear and endothelial antigens in Cogan's syndrome. Lancet, 2002;360:915-21.
Disclosure of Interest None declared