A 32-year-old woman in the third trimester of her fourth pregnancy had a 3-week history of pruritic eruption. The patient first developed a similar eruption 12 years previously, immediately after delivery with her first pregnancy, and had had subsequent episodes in the third trimester every time when pregnant. In the second pregnancy, topical corticosteriods provided limited relief of symptoms. During the third pregnancy the eruption was successfully treated with the local administration of methoxsalen plus UV light (PUVA). No other family member had psoriasis. On examination, the patient had erythematous patches studded with superficial pustules, particularly at the margins, in the groin area, lower abdomen, upper thighs, and neck. The centers of the lesions were impetiginized and crusted (Fig 1). The mucous membranes and nails were normal. Results of a complete blood cell count and chemistry panel were normal. A biopsy specimen taken from an active edge of the lesion