The patient
This 25-year-old man works in the parks department for the local council. He was wearing a sports vest and shorts, showing a deep suntan. He came into the surgery complaining of an intensely annoying itch. He had no history of medical problems and was not taking any medication.
First instinct
This didn't seem to be rocket science. There was a grouped patch of skin lesions on his arm and there were some sporadic lesions elsewhere. For a man who worked outdoors, and whose clothing and suntan suggested he didn't usually cover himself up, insect bites seemed to be the obvious cause.
Differential diagnosis
• Ecthyma
• Infected insect bites
• Insect bites with an allergic reaction
Ecthyma is a bacterial infection of the skin that may be caused by either a staphylococcus or streptococcus. A vesicle appears initially, developing into an ulcer, which will subsequently form a central crust. The lesions tend to be found on the lower limbs.
Although it looked as if these lesions were dark at the centre, I wasn't certain a crust was forming. The fact that the lesions were fairly widespread across the body meant that ecthyma was unlikely.
Insect bites can be challenging to a GP's nerve. Some people's immune reactions
are enormously strong, with large red
areas spreading out from the bite. It's terribly easy in these cases to inappropriately say that the problem
is cellulitis and prescribe antibiotics.
Most of this patient's lesions appeared to have a marked area of redness surrounding them. Although it would have made it easier to say they were infected and prescribe antibiotics, it was highly likely the redness was actually because of an allergic response.
So if these lesions were bites, what was the likely origin? Having exposed skin is a risk factor for getting bitten, and this man's outdoor occupation was certainly increasing the risk.
He also mentioned he was the devoted owner of a labrador. I always make sure I tread carefully whenever questioning the hygiene and flea status of a family pet.
The hidden clue
If I can't find an answer in a case like this,
I will ask the patient their thoughts. He mentioned he was waking up with more lesions than he went to bed with.
So there was the answer – bed bugs.
The skin lesions may have a haemorrhagic centre, which can be seen here and may be seen in threes – as if the bugs are on three meals a day. My recommendation was to check the bed linen for blood spots and to see if any there were signs of bugs themselves. The faeces may manifest on the linen as black dots and there may also be shed skins. If there were any signs, I advised he contact a pest controller, and suggested 1% hydrocortisone cream to reduce the irritation.
Dr Mike Wyndham is a GP in Edgware, north London
