Kimura's disease: a mysterious orbital mass

A male patient in his 20s presented with right lower eyelid swelling and occasional eye ache that was first noticed 3 years ago. Ocular examination revealed a palpable orbital mass, proptosis and restriction of right eye movement. The best-corrected visual acuity in the right eye was 6/24. Fundus examination revealed optic disc hyperemia with a blurred disc margin. Rest ocular examination of both eyes was within normal limits. Haematological examination revealed raised TLC, ESR and eosinophilia. MRI showed a relatively well-defined isointense to hypointense lesion showing heterogeneously post-contrast enhancement involving the belly of the inferior rectus muscle of the right eye. FNAC and histopathology confirmed a diagnosis of Kimura's disease. Oral leflunomide 10 mg/day and prednisolone 40 mg was advised. The swelling started to decrease within 2 weeks of treatment. At 2 months follow-up, the swelling and mass resolved completely and the patient was asymptomatic.