Pruritic urticarial papules and plaques of pregnancy (PUPPP), also known as polymorphic eruption of pregnancy, is the most common rash in pregnant women. It normally occurs in first pregnancies during the third trimester with an average onset of 35 weeks. Thankfully, PUPPP does not usually affect subsequent pregnancies.
Appearance of PUPPP
The rash of PUPPP almost always begins in the stretch marks (striae) of the abdomen. It does not involve the belly button distinguishing it from other common rashes of pregnancy. The rash itself consists of small, red wheals in the stretch marks that grow together to form larger wheals on the abdomen. Sometimes the rash can include small vesicles. Over the next several days, the rash can spread over the thighs, buttocks, breasts, and arms.
The rash is very itchy, or pruritic, hence the name. This condition is harmless to mother and baby, but can be very annoying. It lasts an average of 6 weeks and resolves spontaneously 1 to 2 weeks after delivery. The most severe itching normally lasts for no more than 1 week.
Cause of PUPPP
The cause of PUPPP is unknown. It is not associated with preeclampsia, autoimmune disorders, hormonal abnormalities, or fetal abnormalities. Some investigators suggest that the rapid abdominal wall distension damages connective tissue and causes an inflammatory response. One study has shown that male fetal DNA can be found in skin biopsies of the rash. Since 70% of women with PUPPP give birth to boys, a new hypothesis is that male fetal DNA acts as a skin irritant.
Diagnosis of PUPPP
The diagnosis of PUPPP is clinical, meaning it is based solely on the appearance of the rash. There are no laboratory tests that detect PUPPP. Skin biopsies are not generally performed unless there is a question about the diagnosis.
Treatment of PUPPP
The treatment of PUPPP is symptomatic. High strength steroid creams or ointments, such as clobetasol (Temovate) or betamethasone (Diplrolene), used up to 5 to 6 times a day usually relieve the itching and prevent the spread of the rash. Once the rash is under control, changing to a lower strength steroid used less frequently is advisable. For severe cases, daily oral steroids may be necessary to control itching. Oral antihistamines such as atarax, benadryl, and zyrtec, are generally less effective for itching than steroids, but may be useful at night to help with sleep.