PUPPP Rash · What is it, Risk Factors, and More

Pruritic Urticarial Papules and Plaques of Pregnancy (PUPPP rash), also known as Polymorphic Eruption of Pregnancy (PEP), refers to a benign, pruritic (i.e., itchy) skin disorder of pregnancy that predominantly occurs over the abdomen but may also extend throughout the body. The rash usually begins with the formation of papules, or small, raised bumps, on the skin that can be up to 1 cm in diameter. The small papules subsequently fuse into larger plaques on the skin that can be larger than 1 cm in diameter.

The PUPPP rash is the most common skin condition that occurs in pregnancy and typically affects primiparous individuals in the third trimester of their pregnancy (i.e., weeks 28 until birth). Most commonly, the rash appears at around 35-36 weeks of pregnancy. Less frequently, the rash may appear a short period of time after the delivery of the baby (i.e., postpartum period).

The exact causes of PUPPP are still not identified; however, various theories have been proposed. The most dominant theories are the ones claiming that the rash develops in areas where the skin is stretched, such as the abdomen: an area of the body which extends dramatically during pregnancy. The increased vascularity and damaged collagen of the skin could trigger an immune inflammatory response, resulting in the PUPPP rash. Notably, in about 90% of the cases, the rash develops near areas with damaged connective tissue (i.e., stretch marks). Hormonal changes that occur during pregnancy may potentially also contribute to the development of the PUPPP rash. High levels of progesterone, for example, have been identified in many individuals with PUPPP rash. Lastly, fetal DNA can also be a triggering factor for the development of PUPPP. There are theories that peripheral deposition of fetal DNA (especially of male fetuses) on the mother’s skin, which occurs particularly during the third trimester, could be associated with PUPPP. 

The most characteristic symptom of PUPPP is that the rash appears to be intensely itchy with small, red (i.e., erythematous), and swollen (i.e, edematous) papules and plaques. The lesions can often conjoin to form larger pruritic plaques often surrounded by a blanched (i.e., pale) halo. PUPPP first presents in stretch marks, especially near the belly button (i.e., umbilicus), and within a few days, can spread to the trunk, extremities (i.e., thighs, and arms), and sometimes the buttocks. The rash is typically painless and does not form blisters.

In all cases, the treatment of PUPPP varies according to the individual's symptoms and severity of the rash. The majority of affected individuals achieve satisfactory control with topical steroid creams (e.g., mometasone furoate 0.1%) and oral antihistamines (e.g., diphenhydramine). First- and second-generation antihistamines (e.g., diphenhydramine, chlorpheniramine) are typically safe during pregnancy and can be used as additional therapy to provide relief from pruritus. For more severe irritations, which can disturb the individual's sleep,  a short course of oral steroids (eg. prednisone) can be helpful. 

Further soothing measures, such as cool baths, frequent application of moisturizing creams, and light cotton clothing offer additional symptomatic relief. Recently, intramuscular injection of autologous blood therapy (i.e., injection of an individual's own blood) has been suggested in the literature as a possible alternative treatment, especially in cases of postpartum PUPPP.