Pregnancy Dermatoses

Question 1

Pepmphigoid gestationis epidemiology

Answer 1

• 1:1700-1:50 000
• HLA-DR3 and DR4
• Almost exclusively in pregnancy, rarely trophoblastic tumours (choriocarcinoma)
• In women only
• Have increased risk of Graves disease

Question 2

Pepmphigoid gestationis pathogenesis

Answer 2

• Complement-fixing IgG1 autoantibodies against BP190, BPAG2, collagen XVII
• non collagenous segment closest to the plasma membrane of the basal keratinocyte, NC16A, that constitutes the immunodominant region of BP180
• antibodies also bind to amniotic basement membrane
• Increase in HLA-DR3 and DR4 –> nearly 50% have both
• this implies a high frequency of immunologic insult during gestation
• believed to be initiated by aberrant expression of MHC class 2 antigens, that serves to initiate an allogeneic response to placental BMZ, which then cross-reacts with skin

Question 3

Pepmphigoid gestationis clinical

Answer 3

• Classicaly late pregnancy, but can be any time or post-partum
• Abrupt onset - particularly abdomen and adjacent to the umbilicus
• pemphigoid like - can get pruritic urticarial papule sand plaques, followed by herpetiform vesicles or tense bullae on an erythematous base
• spares mucous membranes
• spontaneous involvement during late gestation is common, but then flares at delivery by 75% –> can be really dramatic
• spontaneously remits during weeks to months following delivery, but occasionally can have a protracted course post partum
• flares and recurrences are common, can be flared by oral contraceptive pill
• recurs in subsequent pregnancies - come on earlier and are more severe
• can ‘skip’ pregnancies in 5-8%
• Neonate:
  
  • 10% develop mild skin involvement due to passive transfer or maternal antibodies, resolves within days to weeks
  • increased risk of prematurity and small for gestational age neonates –> believed to be due to chronic placental insufficiency –> this risk correlates with disease severity

Question 4

Pepmphigoid gestationis histopath

Answer 4

• Minority: subepidermal vesicle
• Normally, a nonspecific mixed cellular infiltrate containing a variable number of eosinophils
• ++ eosinophils
• IF: C3 linear deposition along the BMZ of perilesional skin –>100% of patients, and linear IgG in 30%
• SSS: IgG along the bottom in 30%
• Complement added IIF: circulating anti-BMZ IgG1 autoantibodies
• BP180 serum –> helpful
• Other investigations: increased anti-thyroid antibodies

Question 5

Pepmphigoid gestationis management

Answer 5

• Primary goal: relieve pruritis and suppress blister formation
• Mild: topical steroids, emollients, antihistamines
• Systemic steroids: 0.5 mg/kg daily –> taper as soon as blister formation is suppressed
• Refractive: plasmapheresis
• Anecdotal alternatives: dapsone, tetracycline, nicotinamide, pyridoxine, cyclosporin, MTX, cyclophosphamide, gold IVIG –> none of these are safe

Question 6

Polymorphic eruption of pregnancy epidemiology

Answer 6

• 1/160 deliveries

- primiparous women, doesn’t recur in subsequent pregnancies

Question 7

Polymorphic eruption of pregnancy pathogenesis

Answer 7

• unknown
• reference to increased maternal weight gain? ?rapid, late stretching of abdominal skin may lead to damage of connective tissue and elicitation of an allergic type reaction –> results in striae
• inflammatory response develops cross-reactivity to collagen in otherwise normal-appearing skin
• immune tolerance in subsequent pregnancies might prevent recurrence
• there are other theories too: deposition of foetal DNA, increased levels of progesterone

Question 8

Polymorphic eruption of pregnancy clinical

Answer 8

• pruritic erythematous and oedematous papules and plaques –> appear in abdominal striae, with peri-umbilical sparing
• Onset: 85% last trimester or immediate postpartum 15%
• spares face, palms, soles
• 50% develop polymorphic features as the disease evolves –> target lesions, vesicles, eczematous plaques, widespread erythema
• resolves over an average of 4 weeks
• No maternal of foetal morbidities
• recurrences are unusual except fo subsequent multi-gestational pregnancies (bigger)

Question 9

Polymorphic eruption of pregnancy histology

Answer 9

• non-specific
• spongiosis, acanthosis with hyperkeratosis and parakeratosis
• dermis: perivascular lymphocytic infiltrate with variable degree of dermal oedema, neuts and eos
• early: may look like arthropod bite reactions
• IF negative

Question 10

Polymorphic eruption of pregnancy treatment

Answer 10

• topical steroids and antihistamines
• short course of steroids if really bad
• self-limited