Unilateral eyelid edema is the Romaña's sign of Trypanosoma cruzi infection. This agent causes Chagas' disease and is found in Central and South America.
Courtesy of Joy D Jester, Rolando E Saenz, Lee T Nesbitt, Jr, and WA Krotoski. The Skin and Infection: A Color Atlas and Text, Sanders CV, Nesbitt LT Jr (Eds), Williams & Wilkins, Baltimore, 1995.