Abnormal epidermal changes after argon laser treatment.
 A 26-year-old woman with a congenital port-wine stain on the forehead was treated three times at 2-month intervals with an argon laser.
 Six months after the last treatment, moderate blanching and mild scaling confined to the treated area was observed.
 A biopsy specimen of the treated area revealed a significant decrease in ectatic vessels.
 However, epidermal changes similar to those of actinic keratosis with disorganized cell layers and marked cytologic abnormalities were seen.
 Analysis of peripheral blood lymphocytes for a defect in DNA repair was negative.
 Multiple, argon laser-induced photothermal effects may be responsible for the changes observed in our case and may lead to premalignant epidermal transformation.
