Bilateral extraocular muscles enlargement from Kimura's disease of the orbit

Kimura's disease (KD) is a rare chronic inflammatory disease of unclear etiology, characterized by subcutaneous nodules, mainly in the head and neck region, frequently associated with regional lymphadenopathy. Orbital involvement is infrequent and when it occurs, usually affects the eyelid or the lacrimal gland. We report a case of a 44-year-old man that presented with bilateral slowly progressive proptosis that was initially misdiagnosed as Graves' Ophthalmopathy. 15 months of worsening proptosis and the development of facial and temporal swelling led to further investigation. Computed tomography and magnetic resonance imaging showed enlargement of all recti muscles and diffuse orbital infiltration. An orbital biopsy was performed and was consistent with the diagnosis of KD. Long term oral corticosteroid showed marked improvement of proptosis and facial swelling. This case serves to emphasize that KD should be included in the differential diagnosis of inflammatory diseases of the orbit, even when characterized by predominant involvement of the extraocular muscles.