Balamuthia mandrillaris infection

Balamuthia mandrillaris (B. mandrillaris) is an amoeba that was first discovered in 1990 and has been associated with more than 100 cases of disease since. Infection with B. mandrillaris has been reported in South, Central, and North America, Asia, Australia, and Europe but remains a rare cause of amoebiasis.

B. mandrillaris lives in water and soil and can enter humans through the nasal mucosa, lungs, or breaks in the skin. As in cases of other free-living amoebae (e.g. Naegleria and Acanthamoeba), a history of swimming in freshwater lakes, ponds, and heated swimming pools seems to be common.

Anywhere from weeks to years later (5 to 8 months on average) the infection spreads to the central nervous system causing amoebic encephalitis (inflammation of the brain). Features of amoebic encephalitis include:

• fever
• focal neurological deficits (e.g. double vision has been commonly reported)
• symptoms of meningeal irritation (e.g. neck stiffness, intolerance to bright light)
• symptoms of increased intracranial pressure – e.g. headache, nausea and vomiting, reduced level of consciousness

In 95% of patients, B. mandrillaris encephalitis is fatal.

How does it affect the skin?

The dermatological significance of B. mandrillaris is that a typical skin lesion appears before the infection spreads to the central nervous system. The classical skin lesion is an asymptomatic granulomatous plaque (a nodule made of inflammatory cells), usually located on the central face.

The lesion may enlarge (to involve the entire face in some cases), and occasionally gives origin to smaller satellite lesions. Ulceration occurs at a late stage. Occasionally the lesion may occur on the extremities.

Treatment

Early treatment with a range of oral antifungal, anthelmintic, and antiprotozoal drugs may potentially lead to improved survival.

Draft 18 August 2009