Balamuthia mandrillaris is a free-living amoeba that is known to cause the deadly but rare neurological condition known as Granulomatous amoebic encephalitis (GAE). B. mandrillaris is found in the soil and water.
B. mandrillaris is larger than human leukocytes, thus making phagocytosis impossible. Instead, the immune system attempts to contain them at the portal of entry by mounting a type IV hypersensitivity reaction. They may enter the body through the lower respiratory tract or through open wounds. Upon introduction, the amoeba may form a skin lesion, or may migrate to the brain, causing a condition known as granulomatous amoebic encephalitis,(GAE), which is usually fatal. This granulomatous feature is mostly seen in immunocompetent patients; immunocompromised individuals exhibit a “perivascular cuffing”. Balamuthia-induced GAE can cause focal paralysis, seizures, and brainstem symptoms such as facial paralysis, difficulty swallowing, and double vision.
Balamuthia may also cause a variety of non-neurological symptoms, including skin lesions, which can progress to GAE. Patients experiencing this particular syndrome may report a skin lesion (often similar to those caused by methicillin-resistant Staphylococcus aureus), which does not respond well to antibiotics. The lesion is usually localised and very slow to heal, or fails to heal altogether. In some presentations, this infection may be mistaken for certain forms of skin cancer or leishmaniasis. Balamuthia lesions often cause diffuse swelling.