[Reactivation of sunburn by methotrexate].

For B-All, we treated a five-year-old boy with a combination chemotherapy course including intermediate-dose methotrexate (MTX) with citrovorum factor rescue (CF) two days after a mild sunburn. The insolation inflammation vanished completely, but was reactivated after three days much more severely than the original sunburn, and healed slowly over three weeks. The reactivation phenomenon has previously been described in man and in the guinea pig. It differs substantially from "radiation recall" caused by other cytostatic drugs, as sunburn is not enhanced by MTX applied simultaneously with insolation and is not reactivated if MTX is given more than a week later. Previously irradiated skin regions are spared from the reactivation. Although the phenomenon is not prevented by CF, it can probably be understood as enhanced MTX toxicity to the hyperproliferating basal cell layer of skin after insolation damage. MTX should therefore not be applied for one week after sunburn.