An unusual cause of unilateral epistaxis: a leech in the nose.

Leeches are segmental worms commonly found in fresh water in tropical regions. They can enter the human body via the consumption of contaminated water or through the mouth and nose during washing, generally affecting the upper airway and digestive tract. During the blood-sucking process, the leech releases the anticoagulant enzyme "hirudin" from the wound site into the host's circulation together with an anesthetic to prevent the host from feeling its attachment. Leech endoparasitism is a very rare cause of epistaxis. We report a case of a living leech lodged in the posterior nasal floor in a patient that presented to the emergency department with unilateral epistaxis and a difficult diagnosis.