History
A 31-year-old woman is referred urgently by her local antenatal service complaining of an 8-day history of extensive and severe itchiness associated with an evolving tender erup-tion, which began on the palms of her hands and has spread along the inner aspects of her arms and now involves her trunk. She is at 21 weeks’ gestation with her second pregnancy. Her first child is now 2 years old and was born at 38 weeks +3 days by normal vaginal delivery. Her postpartum period, however, was complicated by a similar widespread pruritic eruption, which blistered within her axillae and upper arms. That eruption began 2 days post-delivery and had responded com pletely to a potent topical steroid within 10 days. She is otherwise well. Her only medication is an iron and folate supplement that was started before conception.
Examination
She is normotensive and continues to slowly gain weight according to her antenatal records. She has widespread urticarial plaques over her palms, medial aspects of her arms, axillae, inner thighs and trunk (Fig. 31.1). There are two tense fluid-filled bullae overlying the erythema in her left axilla. There is no involvement of her mucous membranes. A recent fetal ultrasound scan confirmed her dates to be correct and did not identify any anomalies or abnormalities.
Questions
• What is this eruption and what are the possible differential diagnoses?
• How can you confirm the diagnosis?
• What is the management of this patient?
Medicine
The clinical features in this case (specifically the distribution of the eruption and the pres-ence of blisters) and the patient’s history of a similar, possibly milder eruption occurring at a later stage of a previous pregnancy are highly suggestive of a diagnosis of pemphig-oid gestationis (PG). Other differential diagnoses include pregnancy-specific dermatoses, primarily pruritic urticarial papules and plaques of pregnancy (a non-bullous eruption), and non-pregnancy associated eruptions (e.g. erythema multiforme, acute urticaria, sca-bies, allergic contact dermatitis, bullous pemphigoid, or other immunobullous diseases).
Cholestasis of pregnancy is important to consider when faced with a pruritic patient in her mid-trimester without an eruption. It is associated with elevated serum bilirubin and a significant risk of fetal prematurity. PG is a pregnancy-associated subepidermal immunobullous disease, analogous to bul-lous pemphigoid. The diagnosis can be confirmed by the demonstration of tissue-bound and circulating immunoglobulin G antibodies and complement, targeting the cutaneous basement membrane zone by direct and indirect immunofluorescence studies, and also by subepidermal blisters on histology. There are several considerations when forming a management plan. First, the fetal out-come in PG is generally good; second, it is a self-limiting condition that is expected to remit following delivery (although it may occur earlier and in a more severe form during subsequent pregnancies). However, the intractable pruritus and associated blistering may lead to significant maternal morbidity. Superpotent topical steroids and systemic corti-costeroids are used to control the eruption.
KEY POINTS
• Pemphigoid gestationis (PG) is a pregnancy-associated subepidermal immunobullous disease analogous to bullous pemphigoid.
• PG presents with tense blisters overlying pruritic urticarial plaques.
• PG usually presents towards the end of the third trimester, however it may occur earlier and behave more aggressively in subsequent pregnancies.
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