A case of a patient with IgG4+ plasma cell infiltration, an IgG4-related disease, localized to the auditory ossicles

Immunoglobulin G4+ (IgG4+)-related disease may lead to lesions in various systemic organs. Based on several cases of patients with suspected IgG4-related Mikulicz's disease, the definitive diagnosis of IgG4-related Mikulicz's disease has been established, depending on head and neck lesions (e.g., swelling of the salivary glands, enlargement of the lacrimal glands, and bilateral paranasal sinus shadow mainly of the maxillary sinus). In this study, we report a case with suspected IgG4-related disease based on findings of abnormal auditory ossicles obtained accidently by temporal bone computed tomography (CT). The patient was a 27-year-old woman. She was previously diagnosed with IgG4-related dacryoadenitis and rhinosinusitis, which did not lead to a definitive diagnosis. Her temporal bone CT during her visit to our hospital due to left aural fullness during the course showed a soft tissue density shadow around the left auditory ossicles. Thereafter, the presence of the shadow led to slow progression of decalcification, mainly of the left incus. The relationship between the symptoms and decalcification of the auditory ossicles during the course was unclear. Although steroid therapy was performed because of rapidly progressive, severe sensorineural hearing loss, her hearing did not recover. No central nervous system lesions were apparent in magnetic resonance imaging. The biopsy of the left auditory ossicles, obtained after her informed consent, showed jelly-like osteolytic changes in the left incus, and microscopic results showed infiltration of IgG4+ plasma cells in the tissue of the auditory ossicles. The direct relationship between her severe sensorineural hearing loss and the pathological findings of the auditory ossicles is unclear. However, to our knowledge, this is the first case report of suspected IgG4-related disease that had pathological changes, mainly of the auditory ossicles.