Off food-related illnesses for a while, owing to reader complaints…

A healthy young man spent 3 weeks in northern Vietnam, traveling from Hanoi to Haiphong City, trekking for 3 days in Cat Ba National Park. He and his two companions remained well other than for mild bouts of traveller’s diarrhoea. Although he had fallen a couple of times during the trek, and had to clear away obstructing branches with his hands, he did not recall any major cuts during the trip. He was also bitten by a variety of insects despite DEET application, but none of the bites resulted in any significant reaction that he could recall. He consumed primarily cooked food and bottled water throughout the trip.

Google Maps screen capture of Cat Ba island and national park, Vietnam

Two months later, he incidentally found a small 0.5 cm lump over his right wrist, which he ignored (it was asymptomatic). It gradually increased in size over the course of 6 weeks to 1.5 cm, after which he sought the opinion of a GP. This lump was diagnosed as a ganglion, and he was offered the option of leaving it alone or getting it excised – he chose the former.

Over the next month, he was concerned to note that it continued to increase in size, and was now becoming painful and tender, with overlying erythema. He also noted tingling sensations over the right thumb, with a slight loss of feeling over the same area.

A short course of oral antibiotics (amoxicillin-clavulanate) did not help, and it was finally excised under local anaesthesia. The surgeon noted the presence of thick creamy pus, and had the foresight of sending off pus and abscess wall for various tests, including histology. Bacterial cultures were negative, but the pathologist noted “chronic granulomatous inflammation with few yeast-like organisms – each approximately 4-5 microns – seen”.

Questions:

1. What are the most likely pathogens?
2. How should this young man be managed?

[Updated 21st July 2017]

A very late update, for which I apologise.

Given the travel and exposure history, this is likely to be an endemic mycosis (rather than Candida spp. or Trichosporon spp. infections, for example). I had initially thought that this would be a rare case of cutaneous sporotrichosis, but the fungal cultures were positive for Histoplasma capsulatum instead.

Even though an incision and drainage had been performed, the patient is probably best served by being prescribed a course of oral antifungals (such as itraconazole). In an immunocompetent host, there is no need to perform further investigations looking for disseminated histoplasmosis.