Dermatology in pregnancy — SAQ

Stem

A 30-year-old primigravida at 34 weeks presents with intense pruritus. She has erythematous urticarial papules in abdominal striae and a normal umbilicus. A second patient at 30 weeks has pruritus without a primary rash, worse on palms and soles. A third patient at 28 weeks has periumbilical urticarial plaques with tense vesicles.

Questions

a) Name the most likely diagnosis in each patient and give one key distinguishing feature. (3 marks)

b) List the pregnancy-specific dermatoses and classify them into fetal-benign versus fetal-risk conditions. (4 marks)

^[4]c) What investigations are required for suspected intrahepatic cholestasis of pregnancy and pemphigoid gestationis? (4 marks)

^[7]d) Outline safe initial treatment for PEP/PUPPP, ICP and pemphigoid gestationis, including one drug-dose example. (4 marks)

Model answer

a) Diagnosis and distinguishing feature — 3 marks

• Patient 1: Polymorphic eruption of pregnancy / PUPPP. Key clue: late third trimester urticarial papules and plaques beginning in abdominal striae with the umbilicus usually spared.
• Patient 2: Intrahepatic cholestasis of pregnancy. Key clue: pruritus without a primary rash, especially palms and soles; excoriations may be secondary only.
• Patient 3: Pemphigoid gestationis. Key clue: periumbilical urticarial plaques progressing to tense vesicles or bullae.

b) Classification and fetal risk — 4 marks

• Fetal-benign: atopic eruption of pregnancy and PEP/PUPPP; both can be very itchy but have no disease-specific fetal risk.
• Fetal-risk: pemphigoid gestationis, due to prematurity, small-for-gestational-age risk and rare transient neonatal blistering; intrahepatic cholestasis of pregnancy, due to bile-acid-related preterm birth, meconium and stillbirth risk; pustular psoriasis of pregnancy, due to maternal systemic illness, fetal distress and fetal loss risk if severe.

c) Investigations — 4 marks

• ICP: serum bile acids and LFTs including ALT, AST and bilirubin. Repeat bile acids/LFTs if symptoms persist but initial tests are normal. Evaluate hepatitis, biliary disease, pre-eclampsia/HELLP or drug liver injury when LFTs are marked or presentation is atypical.
• Pemphigoid gestationis: lesional biopsy for routine histology and perilesional skin biopsy for direct immunofluorescence. DIF classically shows linear C3 at the basement membrane zone. BP180 ELISA supports diagnosis where available.

d) Initial management — 4 marks

• PEP/PUPPP: reassure fetal-benign course; emollients, cool compresses, a moderate-potency topical corticosteroid short course, plus an oral antihistamine if needed for itch.
• ICP: involve obstetrics; ursodeoxycholic acid per local protocol for maternal pruritus; monitor bile acids/LFTs and plan delivery by peak bile acids and local guideline.
• Pemphigoid gestationis: potent topical corticosteroid for mild disease; oral prednisolone for moderate-severe blistering, titrated and tapered; obstetric follow-up for fetal growth and neonatal blistering counselling.

Marking traps

• Do not call pruritus without rash physiologic.

• Do not diagnose PEP if the umbilicus is involved or bullae are present.
• Do not say UDCA removes fetal risk in ICP; bile-acid-guided obstetric planning remains essential.
• Do not confuse impetigo herpetiformis with bacterial impetigo or herpes.