A 44-year-old man with bilateral eyelid swelling.

Swollen eyelids are commonly ascribed to allergic conjunctivitis, contact dermatitis, eczema, angioedema, or acute sinusitis. The differential diagnosis extends to thyroid eye disease; blepharitis; Sjögren's syndrome; Churg-Strauss vasculitis; Wegener's granulomatosis; Gleich syndrome; orbital and ocular lymphoid hyperplasia or adnexal lymphoma; idiopathic orbital inflammatory disease/idiopathic sclerosing orbital inflammation; rarely, orbital parasitosis; and IgG4-related diseases. The likely diagnosis proceeds from the more to the less common in patients without a history of allergy or infection. Both ocular lymphoid hyperplasia and ocular adnexal lymphoma must be considered in the differential diagnosis of persistent disease, and neither of these entities can be recognized or differentiated from one another clinically or radiologically. Early diagnosis is essential because therapy may consist of frequent follow-up and/or active intervention. Outcomes in patients treated early and appropriately are often favorable.