The response of psoriatic epidermis and microvessels to treatment with topical steroids and oral methotrexate.

In a previous paper we showed that the microvessels in a psoriatic plaque as studied by electron microscopy returned to normal before the labeling index of the basal cells did during successful therapy with PUVA or the Goeckerman treatment. In this paper we studied the same parameters in 4 additional psoriatic patients: 2 received oral methotrexate and 2 were treated with a topical steroid under plastic wrap occlusion. The labeling index of the basal cells returned to normal in 3 and near normal in 1. The histologic features of the psoriatic epidermis became normal except for mild to moderate acanthosis, but the capillary loops in the dermal papillae retained their venous capillary ultrastructure and showed no signs of reversion to a normal arterial capillary configuration. The lack of response of the dermal capillaries to the topical steroid and oral methotrexate during the initial clinical improvement raises the possibility that the clinical relapses in psoriasis which may promptly follow discontinuation of topical steroid therapy and oral methotrexate may be related to an inability of these drugs to restore the microvasculature to normal in such situations.