Psoralen therapy of vitiligo has produced satisfactory and cosmetically acceptable repigmentation in many patients. However, there have been persistent and, for the most part, unanswered questions regarding the permanency of psoralen-pigmented skin's new pigment. Twenty-one psoralen-treated vitiligo patients who had obtained satisfactory repigmentation were located and examined. Twenty of these patients went 8 to 14 years without further treatment. In the great majority of the patients most of the psoralen-treated areas had retained 90% or more of the new pigment; the repigmentation is thus to be regarded as permanent.
Kenney JA. Vitiligo Treated by PsoralensA Long-Term Follow-Up Study of the Permanency of Repigmentation. Arch Dermatol. 1971;103(5):475-480. doi:10.1001/archderm.1971.04000170009002