Dermatologic Look-Alikes CASE #1
Polymorphic Eruption of Pregnancy
Polymorphic eruption of pregnancy (PEP) is a benign, pruritic self-limiting inflammatory skin condition.1-3 Although the disease was described in 1962 as toxemic rash of pregnancy,4 the first report of PEP often is credited to Thomas J. Lawley, MD, who named the condition pruritic urticarial papules and plaques of pregnancy (PUPPP) in 1979.1,3,5,6 PEP also has been referred to as toxic erythema of pregnancy and late-onset prurigo of pregnancy.3 When a simplified nomenclature system for gestational dermatoses was proposed in 1982, PUPPP became known commonly as PEP.6,7 Estimates for the incidence of PEP range from 1 in 120 to 1 in 200 pregnancies.2,6 Although prevalence estimates range from 0.05% to 0.5% overall, prevalence can be as high as 16% in twin pregnancies and 17% in triplet pregnancies.1,3,6 PEP is more common in White women than in non-White women. It also occurs most commonly in primigravid women in the third trimester, although it can occur after delivery. PEP tends not to recur in subsequent pregnancies.1,3,6 One risk factor linked to PEP is larger belly size, which may explain its association with multiple-gestation pregnancies, increased maternal weight gain, increased newborn birth weight, and male sex of the fetus.1,3,6 One study showed an association between PEP and Rh-positive maternal blood.8 More recently, a case of a pregnant woman with COVID-19 with a clinical presentation consistent with PEP was reported.9 The etiology of PEP is uncertain. It has been suggested that stretching of the abdomen late in pregnancy leads to connective tissue damage; exposure to antigens within collagen could induce an allergic-type reaction that starts within the abdominal striae.1-3 Maternal immune hyperactivity could, thus, predispose some women to PEP.3 Deposition of fetal DNA in skin that causes a graft-vs-host disease state in which fetal lymphocytes attack maternal tissues also is theorized to play a role.1,6 The reaction potentially becomes generalized via cross-reactivity to collagen in normal skin.1 An immune tolerance may prevent PEP from recurring in subsequent gestations.1 Placental factors, human chorionic gonadotropin, sex hormones, high progesterone levels, and increased progesterone receptor immunoreactivity also have been implicated in PEP.1,3 There is no evidence supporting an autoimmune etiology.3 PEP presents predominately on the abdomen, initially within the striae, and characteristically spares the periumbilical region.1
The rash erupts with extremely pruritic erythematous and edematous papules that may coalesce into plaques on the abdomen.The eruption can spread to the extremities, trunk, buttocks, thighs, and back. The majority of patients develop polymorphic features, including annular wheals, target lesions, small vesicles, widespread erythema, and eczematous plaques as PEP progresses.1,3,6 In the early stage of PEP, skin biopsy specimens show edema in the epidermis and upper dermis and a deeper dermal perivascular infiltrate of T-helper lymphocytes, mast cells, neutrophils, and sometimes eosinophils.1,3 Mild focal spongiosis also can be found.1 Biopsies taken from resolving lesions show acanthosis with parakeratosis and hyperkeratosis.1,3 Along blood vessels and the dermal-epidermal junction, histologic studies have found minimal granular deposition of immunoglobulin (Ig)A, complement C3, and IgM.1 However, in most cases, deposits of C3 are not found along the basement membrane of the epidermis, and this can be used to differentiate PEP from pemphigoid gestationis.3
A risk factor for PEP is larger belly size, associated with multiple-gestation pregnancies and increased maternal weight. PEP cannot be diagnosed definitively based on laboratory test results because such findings usually are within normal limits.1,2 Thus, diagnosis is made according to clinical features as well as biopsy, which can be used to exclude similar diseases, especially conditions that may affect the fetus.2,6 Pemphigoid gestationis is the most important diagnosis to rule out because it is associated with premature births and lower birth weights.1,3 Pemphigoid gestationis tends to appear earlier in pregnancy, does not involve striae, involves the umbilicus, and results in positive immunofluorescence of perilesional skin.1,3 Other conditions to rule out include drug-related skin eruptions, urticaria, viral exanthems, and eczematous dermatitis.1,3 Treatment of PEP typically involves topical corticosteroids and oral antihistamines to address symptoms.1-3 In more severe cases with uncontrollable pruritus that may disturb sleep, short courses of systemic corticosteroids can be used. Nonpharmaceutical options for symptomatic relief include cool baths, light cotton clothing, and emollients.1,3 More recently, intramuscular injections of autologous whole blood have shown success in treating postpartum PEP, although limited data support this treatment.1,3 Rarely, cases with especially severe pruritus warrant induction
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