This site is intended for health professionals only

At the heart of general practice since 1960

Snapshot diagnosis - is this lesion on the glans penis an STI?

Dr Mike Wyndham describes a case where his first instinct was of a sexually transmitted infection

Dr Mike Wyndham describes a case where his first instinct was of a sexually transmitted infection

The patient

Jim was a rare attender at the surgery and he looked very reluctant to be there as he gave his history. ‘I've got this itchy rash on my privates. I could never have shown you if you were a woman,' he said – never ceasing to amaze me how strapping men can be so shy. The rash was clearly visible with three lesions on the glans penis. They had a firmish feel to them, which was a surprise as they looked macular to the naked eye.

First instinct

Lesions on the genitals always, as a reflex, make me think this is an STI. However, there are several conditions that can affect the genitals that are not sexually acquired. On this occasion,

I initially broke my golden rule of dermatology – to get a proper history. His embarrassment and the fact that he had a rash had rather thrown my routine.

Differential diagnosis

The rash on the penis pushed me to considering these possibilities:

• genital warts

• psoriasis

• lichen planus

• scabies

• fixed drug eruption

• syphilis.

Getting on the right track

Genital warts tend to form flattish lesions and look less inflamed than this gentleman's rash. Syphilitic lesions on the penis tend to be ulcers. The glans seems to be a popular place for fixed drug eruptions but he had not had any medication in a long time. Lichen planus on the penis is usually an annular rash. Psoriasis is not usually nodular. So scabies became the likely culprit, particularly as it causes itching.

The hidden clue

My uncertainty was a wake-up call to get that proper history. ‘Any rash elsewhere?' I inquired. ‘Yes', he replied, ‘on my trunk, arms and hands.' Inspection of the hand revealed a burrow, clinching the diagnosis of scabies (see pic of the hidden clue right). Malathion was the treatment for all areas.

Dr Mike Wyndham is a GP in Edgware, north London

 

What's causing this itchy rash on the glans penis? What's causing this itchy rash on the glans penis? The hidden clue The hidden clue

The hidden clue

Rate this article 

Click to rate

  • 1 star out of 5
  • 2 stars out of 5
  • 3 stars out of 5
  • 4 stars out of 5
  • 5 stars out of 5

0 out of 5 stars

Have your say