This 58-year-old man showed me his left foot and said “still no better doc, perhaps I need more antibiotics?” His foot had been troubling him for nearly two months. He had no idea what caused it, but he knew it hurt and it was interfering with his job in construction. Like most of his friends, he smoked and he enjoyed a few pints after work. He had the usual aches and pains that go with his line of work, but this foot problem was different. It had got gradually more sore over seven weeks, despite him resting it. He was still going into work in his steel toe-cap boots – with difficulty - because he didn’t get sick pay.
Differential diagnoses
- Gout
- Cellulitis
- Bony pathology
Gout is caused by the deposition of monosodium urate crystals in the articular or peri-articular tissues. Crystals form more easily at low temperatures, which explains why it affects peripheral joints rather than proximal. Serum urate levels can be normal or low in acute gout, so I didn’t measure them in this patient.
Cutaneous infection with Streptococcus pyogenes or less commonly Staphylococcus aureus gives the classic cellulitis infection. A microbiologist told me that topical therapies for cellulitis are pointless because the infection is within the skin, not on top of it, but I sometimes give patients some Dermol just to moisturise the skin.
A bony malignancy could fit with this presentation, although I would have thought he’d be unable to weight bear fully if he had an underlying tumour or even a fracture.
Getting on the right track
At his first presentation to us, six weeks earlier, another GP had given some indometacin and colchicine for gout. There was partial alleviation of the pain, but certainly no cure.
When he presented again another colleague had prescribed a two-week course of flucloxacillin on the presumption of cellulitis. But this hadn’t given him any relief. So by the time he saw me, I had the benefit of being able to rule out two of the differentials. So, to the patient’s confusion, I sent him for an X-ray.
The same day, after the X-ray, the patient returned to me saying the radiographer had told him the X-ray was clear and to ‘get some more antibiotics because it’s just cellulitis’. But I wasn’t convinced. Ten days later the formal report from a consultant radiologist showed a Lisfranc fracture - a fracture dislocation between the metatarsals and the tarsal bones.
I referred the patient to the fracture clinic and after two months in an airboot and some physiotherapy, his foot was back to normal.
This just goes to show that fractures can occur without an overt trauma.
Dr Oliver Starr is a GP in Stevenage, Hertfordshire
