Kimura's disease (KD) is a rare, chronic inflammatory disorder, which is characterized by tumor-like masses mainly located in the head and neck region. Extraocular muscle involvement in KD is uncommon. We report a case of KD that involved both the extraocular muscles and buccal area. A 13-year-old male presented to our clinic with a two-year history of exophthalmos of the left eye and facial swelling. Facial CT and MRI showed a 1.5 x 1.5 cm(2) soft tissue mass located at the left masticator and buccal area, exophthalmos of the left eye, and diffuse thickening of the left extraocular muscles. We performed a lateral rectus muscle incisional biopsy of the left eye. Oral methylprednisolone therapy was initiated and tapered following the incisional biopsy. Histopathologic findings of the lateral rectus muscle incisional biopsy showed abnormal vascular proliferation with marked eosinophilic infiltration in hypertrophied collagenous tissue. Post-operative histopathologic findings of the facial mass confirmed the diagnosis of KD. Although KD with extraocular muscle involvement is uncommon, an ophthalmologist can diagnose KD by the clinical presentation of exophthalmos, eyelid swelling, and an orbital massas well as by histological examination of a biopsy of the orbital mass.
Keywords: Exophthalmos; Extraocular muscle; Eyelid swelling; Kimura's disease.