So this 9 year old boy came through the clinic the other day. He sat in the chair closest to the desk. Good start. I started with “G’day, what can we do for you today fella?” Response *look straight at Mum* Ah well, can’t win em all!
Anyway, he had been having trouble with a non healing scab/wound on his proximal thumb. It had started about a week or two ago when he thought that something might have bitten him. After that it swelled up and went a bit red. Mum said that it only lasted for 2-3 days and had got better so she didn’t get it checked out. After a week some yellow blisters appeared and then popped with some clear/yellowish fluid drained. Since then it hasn’t really got much better. His immunisations were up to date and there wasn’t anyone sick at home or at school. Feel free to comment below and weigh in…
Description of the lesion?
Im going to go with Penny’s description of an inflamed lesion on the proximal right thumb that has some crusted yellow sores. I wondered whether the middle reddish part of the lesion was an initial injury or bite that kicked off the infection.
Preferred diagnosis with differentials?
From the history and from the looks of the lesion, impetigo was my first thought. Not sure what the cause here might have been, usually a scratch or insect bite. Dr Penny Wilson makes the good point that it could be due to an area of prolonged irritation such as with a thumb sucker. DermnetNZ also mentions that scratched eczema could also present like this. Scabies and head lice should always be considered also.
Investigations and treatment options?
For this chappy, I took a bacterial swab and started him on oral Flucloxacilin. I suppose that given the localised nature of the infection, I probably could have got away with a topical antibacterial such as mupirocin (Bactroban). Dr Mel Clothier added that a viral swab to rule out underlying HSV may be helpful. Apart from oral antibiotics there are a few simple measures that both the Therapeutic Guidelines and DermnetNZ suggest including:
- Soak moist and crusted areas with cloth containing vinegar/tepid water mixture (1 cup in a litre)
- Antiseptic or antibiotic ointment if simple case
- Treat carriers: full body bath with small amount of bleach and/or mupirocin per nostrils
- Avoid close contact, cover sores, separate linen/towels
- Non infectious once crusts dried out
In the end, Mum found that the lesion had reduced in size, was healing well and didn’t need further treatment. She sent me this photo which highlighted the benefit of teaching our patients and parents to take good images! The microbiology results showed Staphylococcus aureus and was sensitive to penicillins.
More images of impetigo from DermnetNZ.
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