A case of autoimmune progesterone dermatitis diagnosed by progesterone pessary

Autoimmune progesterone dermatitis is a rare, cyclical eruption that occurs in the luteal phase of the menstrual cycle and during pregnancy. Many manifestations have been reported including cyclical eczema, urticaria, erythema multiforme, stomatitis and even anaphylaxis. The condition spontaneously resolves after menopause. As histopathology is non-specific, the diagnosis rests on history with precipitation of the eruption by a progesterone challenge, usually by the intradermal, intramuscular or oral route. We present the case of a 34-year-old woman with a premenstrual papular and eczematous eruption that was exacerbated after pregnancy. Biopsy showed subacute spongiotic dermatitis. To confirm the diagnosis, we used an intravaginal progesterone pessary as a provocation challenge. There was recurrence of the rash 12 h after insertion of the pessary with spontaneous resolution thereafter. We propose that use of a progesterone pessary is an effective tool in the diagnosis of autoimmune progesterone dermatitis.