A Case in Which the Endoscopic Denker's Approach Was Useful in the Diagnosis of IgG4-Related Ophthalmic Disease.

IgG4-related disease (IgG4-RD) is a chronic inflammatory condition characterized by elevated serum IgG4 levels, infiltration of IgG4-positive plasma cells, and fibrosis in various organs. We report the case of a 76-year-old man who presented with left-sided proptosis. Computed tomography revealed a mass lesion in the left orbit. An initial biopsy via a transnasal approach under local anesthesia was inconclusive. Although endoscopic sinus surgery was performed under general anesthesia, a definitive diagnosis could not be obtained. The lesion continued to enlarge, and subsequent ophthalmologic examinations revealed progressive optic nerve compression. Therefore, tumor resection was performed again under general anesthesia using the endoscopic Denker's approach. The tumor was successfully resected without complications. Histopathological findings led to a diagnosis of probable IgG4-related ophthalmic disease (IgG4-ROD). Following surgery, the residual lesion enlarged again; however, a three-day course of steroid pulse therapy resulted in reduction of the lesion and improvement of optic nerve compression. The patient has remained relapse-free. While 81% of IgG4-ROD cases involve the lacrimal gland, other orbital structures such as the pterygopalatine fossa, trigeminal nerve branches, extraocular muscles, orbital fat, eyelids, and nasolacrimal duct can also be affected. In cases without lacrimal gland involvement, the optimal approach for obtaining diagnostic biopsy specimens should be considered individually. Although there is no consensus on the required volume of tissue for diagnosis, we believe that aggressive resection of the central lesion is necessary for accurate diagnosis. The endoscopic Denker's approach facilitates wide exposure and resection of far lateral maxillary sinus lesions, enabling both decompression and definitive diagnosis, which can lead to appropriate subsequent treatment.