IgG4-related disease of the infratemporal fossa: A case report

IgG4-related disease is a relatively new disease entity characterized by elevated serum IgG4 levels and marked infiltration of IgG4-positive plasma cells in mass lesions. IgG4-related disease of the head and neck region is often associated with the salivary glands, and Küttner's tumor and Mikulicz's disease of the salivary glands may also be IgG4-related diseases. We encountered a patient with an inflammatory pseudotumor (IPT) of the infratemporal fossa, which was histopathologically confirmed to be IgG4-related disease. The patient was a 53-year-old man who presented with tenderness of the right upper jaw, ocular pain, and trismus for approximately 3 months. Imaging revealed a lesion with unclear borders extending from the infratemporal fossa into the right orbit. Soft tissue tumor was suspected and biopsy was performed under general anesthesia. Histopathological examination revealed plasma cell infiltration and fibrosis. Immunohistochemistry revealed prominence of IgG4-positive plasma cells and confirmed the diagnosis of IgG4-related disease. The patient responded well to steroidal therapy, with pain and trismus resolving. Imaging revealed marked reduction in the size of the mass. The patient is currently under observation on low-dose oral prednisolone with no evidence of relapse.