Otosclerosis is a bone remodeling disorder of complex etiology. Persistent measles virus infection of the otic capsule could increase the expression level of measles virus receptors (CD46) on the osteoclasts and endothelial cells of the otosclerotic foci. Presence of measles virus RNA was demonstrated in the footplates of histologically diagnosed otosclerotic patients by RT-PCR; however, no reports were available about the CD46 expression pattern and level in otosclerosis. Nucleic acid was extracted from stapes footplates of clinically otosclerotic patients (N = 116). Genomic RNA of measles virus was amplified by RT-PCR. Amplification results were correlated with postoperative histologic and CD46 specific immunhistologic findings. Among 116 stapes fixation cases, 87 otosclerotic stapes contained measles virus RNA. Histology for virus negative stapes (N = 29) represented degenerative disorders with heterogeneous histopathology. Active otosclerosis was featured by increased numbers of osteoclasts showing strong CD46 expression. In virus negative, non-otosclerotic stapes fixation and in normal stapes footplates weak CD46 immunoreaction was demonstrated on the osteocytes and fibroblasts. In otosclerosis, it is reasonable to assume that measles virus increases the expression level of its own cellular receptor. Furthermore, intensive CD46 reaction could relate to active virus replication and continuous receptor internalisation. Otosclerosis is a disease of disturbed osteoid turnover due to persistent measles virus infection and special CD46 receptor pattern of the otic capsule.
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