Pneumosinus dilatans of the ethmoid sinus presenting with exophthalmus: a case report and review of the literature.

Pneumosinus dilatans (PSD) is a rare condition of unknown aetiology in which there is enlargement of the paranasal sinuses by air, where the affected sinus expands beyond the normal boundaries of bone without thinning of its bony walls. The case of a 28 year old male with PSD, who had gradually increasing exophthalmus and diplopia, is presented and characteristics of this condition are reviewed with literature data.