Photodynamic therapy for flat warts arising on a tattoo

Cutaneous warts are common benign lesions caused by human papillomavirus (HPV). While treatments such as cryotherapy, laser therapy, and electrosurgery can be effective, they may be unsuitable for warts over tattooed skin due to the risk of pigmentary alterations and scarring. Photodynamic therapy (PDT) is a non-invasive treatment that selectively targets HPV-infected keratinocytes, minimizing damage to surrounding tissue. However, no studies have specifically evaluated PDT for warts on tattooed skin. We report the case of a 25-year-old male with multiple flat warts over a long-standing tattoo on his forearm, successfully treated with three sessions of conventional PDT using 10 % aminolevulinic acid (ALA) ointment (Biosynth AG, Staad, Switzerland). Irradiation was applied with diode red light at 630 nm in wavelength (S630, Alpha Strumenti, Milan, Italy). The light source was positioned at 50 mm from the skin surface, which gave a skin irradiance of about 160 mW/cm². The light exposure period was 8 min, resulting in a total light dose of 75 J/cm². The procedure was well tolerated by the patient, who complained of only a mild burning sensation during light exposure. At three-month follow-up, complete wart clearance was observed, with no tattoo distortion or recurrence at one year. This case highlights the potential of PDT as a first-line treatment for warts in cosmetically sensitive areas, offering effective viral clearance while preserving tattoo integrity. Further studies are warranted to validate its efficacy in larger cohorts and establish standardized treatment protocols for tattooed skin.