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What has caused this man's long-lasting papular rash?

Dr Keith Hopcroft explains how a rash that looked like eczema was finally diagnosed

 

The patient

‘I'm getting really fed up with this rash,' said my next patient, a 30-year-old man who rarely attended the surgery. ‘I've had it for years now and nothing will shift it.'

He had no relevant medical history and was on no medication. A brief interrogation revealed that the rash had started in his teens and gradually got worse. It was now affecting his chest, neck and upper back. It was mildly itchy, but his main concern was the appearance.

‘I blame my dad,' he continued. ‘He had something very similar.'

Sadly, his father had died a few years before in a car accident – and had never sought advice about his skin condition. The patient's two siblings were unaffected.

First instinct

Examination revealed a well-demarcated papular rash that was most marked on his neck – but also present on his chest and back. Other skin areas were unaffected and he seemed otherwise well in himself.

The distribution was fairly characteristic of seborrhoeic eczema – and the mild irritation fitted with this diagnosis.

Differential diagnosis

• Seborrhoeic eczema

• Keratosis pilaris

• Multiple warts

• Obscure dermatoses.

Although the distribution fitted for seborrhoeic dermatitis, I was far from convinced. The appearance was odd and the history unusually long.

Keratosis pilaris can look similar, and can become apparent in childhood or the teenage years – but is normally distributed along the upper arms and thighs. Besides, it tends to improve into adulthood.

Close inspection of the lesions showed a distinctly warty appearance – but I've never encountered warts as disseminated as this, and could not imagine this could be the explanation in someone who was well.

The hidden clue

I was not too surprised when, on review, he had failed to respond to the steroid/ antifungal combination cream I'd prescribed. I had tried this more in hope than expectation.

Two factors now suggested a precise diagnosis was going to require a specialist opinion. First, his reiteration of his family history: I hadn't taken much notice of his comment about his father, imagining that it might be a false trail.

And, second, the results of a further examination – this time including his nails, which, of course, should be examined in any challenging dermatological case. They were symmetrically dystrophic, and he admitted they tended to split and break easily.

He hadn't volunteered any nail symptoms as he hadn't thought them relevant. These factors suggested a significant familial skin disorder. Next stop: a dermatologist.

Getting on the right track

Putting all the clues together – and with the benefit of having seen a few previous cases – the dermatologist suggested a likely diagnosis of Darier's disease. This autosomal dominant disorder of hair follicles was confirmed on skin biopsy – and, at last, the patient is getting some relief thanks to topical salicylic acid and isotretinoin.

Dr Keith Hopcroft is a GP in Laindon, Essex

Papular rash on the neck Papular rash on the neck

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