Otosclerosis--an inflammatory disease of the otic capsule of viral aetiology?

Fragments of otospongiotic and otosclerotic footplates were investigated by immunohistochemical methods. Antibodies IgG, IgA, IgM were found to be bound to the vascular connective tissue of the resorption lacunae, IgG also to osteocytes. The application of antibodies against mumps, measles and rubella antigens showed the expression of the relevant viral antigens in the large cells of the resorption lacunae, in the vascular connective tissue, and in osteocytes, osteoclasts and chondrocytes, present in or around the otospongiotic areas. In the sclerotic stage only the perivascular connective tissue and chondrocytes have expressed viral antigens whereas IgG was restricted to the osteocytes of the sclerotic focus and to the residual perivascular tissue. Two footplates with postinflammatory sclerosis serving as controls revealed only IgG in some chondrocytes. Healthy footplates showed neither a deposition of antibodies nor any expression of viral antigens. These results favour a viral aetiology of otosclerosis as an inflammatory vascular reaction of the otic capsule initiated or caused by the viruses of measles, rubella and mumps.