The "Heart Sign": An Early Indicator of Dose-Dependent Doxycycline-Induced Phototoxicity.

Oral doxycycline is an antibiotic commonly used for the treatment of inflammatory acne in adolescents. Dose-dependent phototoxicity, unrelated to dose duration, is a well-known complication of its use. We present three adolescents who developed bilateral phototoxic rashes on the dorsal thenar spaces of their hands while taking doxycycline for their acne. Identification of the "heart sign" rash as a specific doxycycline-related phototoxic reaction should alert clinicians to the need for prompt intervention, including sun protection counseling and a possible change in antibiotics, in the uniquely vulnerable adolescent population. Early recognition may allow patients to avoid future, more widespread phototoxic drug reactions.