A 25-year-old female with an Unusual Ulcer

This case has been inspired by events in the Torres Straits and details have been changed to ensure patient anonymity.

History

A 25-year-old female presented to the an outer island primary healthcare centre with a non-painful leg ulcer. She didn’t remember having a bite, sting, scratch or injury to the area and said it had been slowly getting worse for the past month.  Initially it had some pus, but now just a haemoserous ooze. She didn’t have any other ulcers and was systemically well. The diligent nurse at the time took a swab for microscopy, culture and sensitivity and gave her a course of flucloxacillin for five days. The patient returned to the clinic five days later having completed her course of antibiotics. The wound still hadn’t healed. The swab results were still pending and so under the guidance of the on call doctor who thought she may have MRSA, was given a course of Bactrim (trimethoprim/sulfamethoxazole).

Clinical Findings

This is what the lower leg ulcer looked like after a course of both flucloxacillin and Bactrim. The patient always had observations within normal limits during each clinic visit.

What are your differential diagnosis?

How would you approach this patient?

The Case Continued…

By now the ulcer had persisted for almost six weeks! The initial swab had cultured fully sensitive staphylococcus aureus. Clearly that had been treated and the wound would have healed if this was the culprit. There was no trauma to explain this as a post-traumatic ulcer; a vascular ulcer would be unusual for this otherwise well 25-year-old; Yaws, a common occurrence in Paupa New Guinea was negative and a subsequent biopsy ruled out a neoplastic cause. Amongst all those further investigations, a clever doctor had also taken a swab for Mycobacterium Ulcerans which eventually returned positive. She was treated with 8 weeks of rifampicin and clarithromycin and the wound healed fully, luckily with no sequelae.

Pearls from the Torres

You may be more familiar with the colloquial terms Buruli, Daintree or Bainsdale ulcer. They are one and the same thing: M. Ulcerans. A slow growing infection that leads to the destruction of skin and soft tissue, resulting in chronic ulcers. It is diagnosed by PCR and antibiotics are the mainstay of treatment under specialist guidance. Those untreated can have significant functional disability.

The most recent outbreak in Queensland was in 2011, where 54 cases were identified; most of these were in the Daintree area (no surprises there!). Cases of M. Ulcerans in the Torres Straits are uncommon but an important differential to consider when managing ulcers in this region. Although typically found in tropical and subtropical climates such as Africa and South America, there have been recent outbreaks in Victoria which have prompted calls for more research in this area. Here in the Torres we are currently investigating the epidemiology Mycobacterium Ulcerans infections in our region – watch this space.

Further Reading

Treatment and prevention of Mycobacterium ulcerans infection (Buruli ulcer) in Australia: guideline update

World Health Organisation Buruli ulcer

What GPs need to know about the flesh-eating Buruli ulcer