Pemphigoid Gestationis
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Direct answer
Pemphigoid gestationis is a rare autoimmune blistering disease of pregnancy caused by IgG antibodies against BP180, typically beginning in the second or third trimester or in the early postpartum period. It presents with intensely itchy urticarial plaques around the umbilicus that progress to tense vesicles and bullae, and direct immunofluorescence shows linear C3 at the basement membrane zone. Despite its older name, herpes gestationis, it has no viral cause.
What you must remember
- Nomenclature: herpes gestationis is a misnomer, since the disease is autoimmune and has no viral cause.
- Antigen: BP180, also called type XVII collagen, with autoantibodies targeting its NC16A region.
- Onset: second or third trimester or early postpartum, with the umbilicus typically involved first and then spreading.
- Morphology: urticarial papules and plaques that evolve into vesicles and bullae, with intense itch as the rule.
- Immunofluorescence: linear C3 at the basement membrane zone, with IgG found in only some cases.
- Fetal risk: preterm birth and small-for-gestational-age infants are reported, so obstetric follow-up matters.
- Neonate: transient neonatal pemphigoid can occur because maternal IgG crosses the placenta, and it usually resolves spontaneously.
- Recurrence: flares are common in later pregnancies and often start earlier and sometimes more severely.
Where candidates lose marks
Examiners test whether candidates treat this as a viral rash, a benign pregnancy dermatosis or an autoimmune disease with fetal consequences.
- Trap: labelling any periumbilical itchy rash in pregnancy as herpes gestationis and treating it as viral Correct: the disease is autoimmune, so antivirals do nothing and a biopsy with direct IF confirms it.
- Trap: assuming the rash carries no fetal risk Correct: preterm birth and small-for-gestational-age infants are reported, so obstetric surveillance is needed.
- Trap: using systemic steroids by default for mild disease Correct: mild disease is usually controlled with potent topical steroids, which limits systemic exposure in pregnancy.
Frequently asked questions
Why is pemphigoid gestationis also called herpes gestationis?
The older name herpes gestationis persists in many texts, but it is a misnomer because the disease has no viral cause. It is an autoimmune reaction to BP180, so candidates should recognise both names.
Which antigen is targeted in pemphigoid gestationis?
Pemphigoid gestationis is caused by autoantibodies against BP180, also known as type XVII collagen, particularly its NC16A region. This explains the linear basement membrane pattern seen on direct immunofluorescence.
Can pemphigoid gestationis affect the newborn?
Yes, transient neonatal pemphigoid can occur because maternal IgG crosses the placenta. Affected neonates usually recover without lasting harm, so paediatric review is the key step after delivery.
Does pemphigoid gestationis recur in later pregnancies?
Pemphigoid gestationis often recurs in later pregnancies, and flares may begin earlier and be more severe. Counselling and early specialist planning are therefore important for future pregnancies.
What is the main differential diagnosis of pemphigoid gestationis?
Polymorphic eruption of pregnancy is the main differential, since it causes intensely itchy papules and plaques within striae and spares the umbilicus. Pemphigoid gestationis differs by its periumbilical onset and positive direct immunofluorescence.