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What's behind this woman's intolerably itchy rash?

The itching on a pregnant woman’s abdomen had become intense – Dr Mike Wyndham explains how he found the cause

The itching on a pregnant woman's abdomen had become intense – Dr Mike Wyndham explains how he found the cause

The patient

This woman was 28 weeks' pregnant when she first presented with an extremely itchy rash on her abdomen, arms and legs. It had been getting rapidly worse and was particularly bothersome at night. She had resorted to hot showers which seemed to only make things worse. The rash was bright red and slightly raised. Clinically, it resembled an acute eczema, although I couldn't identify why she may have developed it. I suggested using betamethasone 0.1% ointment twice a day with an emollient at other times.

A week later she came in again. The treatment had made no impact and, in fact, things were much worse. The itching had become intense and she hadn't slept for much of the previous week. The rash appeared more profound on her abdomen and some blisters appeared to be developing. Surprisingly, this could be seen on the feet as well as the arms. There was a pustular appearance to the rash on the feet which was the latest of the skin lesions.

First instinct

Although I'd been confident about the eczema diagnosis based on the symptoms, she had never suffered eczema before and there was no obvious precipitating cause. But what was the explanation for the blisters? They were tense and resembled pemphigoid.

Differential diagnosis

• Pustular psoriasis (appearance of the foot)

• Pemphigoid gestationis (formerly herpes gestationis)

• Pruritic urticarial papules and plaques of pregnancy (PUPPP)

• Bullous pemphigoid

The appearances on the feet certainly had the appearance of pustular psoriasis with the vesicles at different stages but the rest of the rash did not resemble a generalised pustular psoriasis. Bullous pemphigoid usually affects people in the middle to older age group and so made the diagnosis unlikely.

PUPPP – also known as polymorphic eruption of pregnancy – usually affects the striae and most often does not involve the umbilical region. The vesicles are small which is against the appearance seen on the foot and limbs.

Getting on the right track

Pemphigoid gestationis is a condition that can occur at any stage in pregnancy. Vesicles may coalesce to form blisters and the periumbilical region is affected in around 90% of women. The rash tends to spread peripherally affecting the face, palms and soles.

So the history and appearance of the rash fitted strongly with the diagnosis. But it's thought to occur in perhaps only one in every 25,000 pregnancies and so a skin biopsy was needed. The diagnosis was confirmed and the patient was started on prednisolone.

The condition may recur in subsequent pregnancies and with the use of oral contraception.

Dr Mike Wyndham is a GP in Edgware, north London

Abdominal rash Foot rash

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