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Snapshot diagnosis - what's this annular rash on the glans?

Dr Mike Wyndham shares another interesting case from his files

Dr Mike Wyndham shares another interesting case from his files

The patient

This 46-year-old man presented with a slow-growing rash on his glans penis. It was not causing him any symptoms. He had no rash anywhere else. He was a sexually active single male and was very concerned that he had contracted an STI.

First instinct

My view was that this did not appear to be an STI. It did not look right for the flat lesions of warts or the vesicles of herpes simplex.

A syphilitic chancre usually starts as a macule and will then ultimately ulcerate and this man's skin was intact.

Differential diagnosis

The skin lesion had an annular appearance and the following might be considered as diagnoses:

• lichen planus

• granuloma annulare

• ringworm

• psoriasis

• pityriasis rosea.

Getting on the right track

The herald patch of pityriasis rosea tends to have a rose-coloured border and perhaps be flatter. Psoriasis tends to be more scaly. Ringworm usually has a reddish border. Granuloma annulare tends to occur over bony prominences. This left annular lichen planus as the most likely diagnosis.

The hidden clue

There was no rash visible elsewhere on the body. However, inspection of the buccal mucosa revealed white patches along with characteristic white streaks typical of Wickham's striae compatible with oral lichen planus.

Outcome

The diagnosis was lichen planus. As the patient was asymptomatic for both lesions, no treatment was required.

Dr Mike Wyndham is a GP in Edgware, north London

What's this annular rash on the glans? What's this annular rash on the glans?

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