Tropical ulcer is also called tropical phagedaenic (phagedenic) ulcer. This is a painful, rapidly enlarging sore, usually found on the lower limb of an individual living in a hot, humid tropical region. Phagedaenic refers to its appearance
as if it was gnawed.
What is the cause of a tropical ulcer?
Multiple factors play a role in causing tropical ulcers.
- There is initially some form of trauma/injury to the skin, often as minor as a scratch or an insect bite. Rural labourers who do not wear adequate protective clothing and footwear are at increased risk.
- Poor nutrition, poor hygiene, and chronic diseases such as malaria and intestinal parasites also increase the risk of a tropical ulcer developing.
- A variety of bacteria are found to be present; Fusobacterium species are almost always present in the early stages; Bacillus fusiformis and Treponema vincenti are often found in the late stages. Other bacteria such as Escherichia coli and Enterococcus species may be present.
Clinical features of a tropical ulcer
The ulcer is initially circular, superficial, very painful, and has purple edges. It enlarges rapidly across the skin and down into deeper tissues such as the muscle or even the periosteum (the fibrous membrane covering the surface of bones). The ulcer may reach several centimetres in diameter after a couple of weeks. The edges become thickened and raised and the central crater may become necrotic (blackened due to death of tissue) and foul-smelling.
It is important to rule out other causes of ulcers such as cutaneous leishmaniasis, atypical mycobacteria, pyoderma gangrenosum, and venous disease. Swabs can be taken from the base and edges of the ulcer to determine the type of bacteria present.