January 2018 | Case of the Month

The diagnosis is Polymorphic eruption of pregnancy, also known as PUPPP (Pruritic Urticarial Papules and Plaques of Pregnancy).

• History - polymorphic eruption of pregnancy usually occurs in the first pregnancy with symptoms presenting in the last three months, especially the last five weeks. It can rarely begin after pregnancy. The itching tends to be intense
• Distribution - lesions arise in the stretch marks around the umbilicus. The umbilicus itself is frequently spared. The rash spreads to involve the buttocks and thighs, and sometimes the arms and legs. Lesions on or above the breasts are rare
• Morphology - multiple urticated papules and plaques. Less commonly vesicles, target lesions and polycyclic erythematous patches
• Resolution - symptoms continue until delivery then usually resolves within a few weeks. Rarely, it may persist for longer. In some cases, this relates to retained placental products

The main differential diagnosis is pemphigoid gestationis, but this often differs in the following ways:

• May arise at any time between four weeks gestation and five weeks postpartum, with the majority presenting in the second and third trimesters
• Lesions arise characteristically around the umbilicus. Within days to weeks the rash spreads to other parts of the body including the trunk, back, buttock, and arms
• The rash usually arises as urticated papules, plaques, target lesions and annular wheals. This is followed by the development of vesicles and large, tense blisters

For more information please refer to the chapter on Pregnancy related skin conditions.