PDT uses a medication and light together to cause injury to a target. The medication is given and then light is directed at the desired area of treatment to achieve an effect. PDT has been used to treat some skin conditions including pre-cancers and skin cancers. Using PDT or PDT immediately followed by PDL therapy may improve PWS lightening. At this time, both PDT and PDT + PDL therapy for treatment of PWS is investigational. The type and amount of medication and light which may be used to treat PWS is not known, and is likely to be different than those used for other PDT treatments.