Balamuthia mandrillaris (and Sappinia)
- Parasite
- For completeness
A soil amoeba that enters through skin wounds or the lungs and reaches the brain slowly. It often starts as a skin plaque on the face.
Also called: Sappinia pedata, granulomatous amoebic encephalitis
Quick facts
- Type
- Parasite · Free-living amoebae
- Gram / shape
- Pleomorphic trophozoite with long pseudopods
- Spread
- Soil or dust entering skin wounds
- Causes
- Granulomatous amoebic encephalitis · Sappinia
- Treatment
- Long multidrug combinations that may include pentamidine
At a glance
- Shape
- Pleomorphic trophozoite with long pseudopods; double-walled cyst like Acanthamoeba
- Family
- Balamuthiidae
- Type
- Free-living amoeba
- Stain
- H&E of biopsies; immunofluorescence or immunoperoxidase of tissue
- Size
- Trophozoite about 15 to 60 µm; cyst about 10 to 25 µm
Morphology
- Trophozoite of variable shape with long branching pseudopods; usually one nucleus.
- Round cyst with two walls visible by light microscopy and no pores; hard to tell from Acanthamoeba without special tests.
- Sappinia: trophozoites and cysts with two nuclei pressed together.
Transmission
- Soil or dust entering skin wounds, or inhalation into the lower airways.
- Spread through the blood to the brain.
- Rarely through an organ from an infected donor; otherwise not person to person.
Reservoir: Soil and dust; also isolated from water
Isolation precautions
What the care team adds to standard precautions.
- Standard
Life cycle
- It lives in soil as a trophozoite and forms cysts when conditions are unfavorable.
- Trophozoites, the infective form, enter through broken skin or the airways.
- They multiply in the skin or lungs and cause granulomatous lesions.
- They reach the brain through the blood and cross the blood-brain barrier.
- Trophozoites and cysts are both found in infected tissue.
Virulence factors
- Binding to brain microvascular endothelium and crossing of the blood-brain barrier.
- Necrotizing, hemorrhagic vasculitis with granulomas (which may be poor in immunosuppressed patients).
- Cysts resist drugs and immune attack.
Diseases it causes
- Granulomatous amoebic encephalitis: subacute to chronic, over weeks to months; fatal in about 9 of 10 cases. Free-living amoeba infections (Naegleria meningoencephalitis, Acanthamoeba) →
- Cutaneous balamuthiasis: a painless, enlarging plaque, often on the central face (nose, cheek), that can precede brain disease by months. Free-living amoeba infections (Naegleria meningoencephalitis, Acanthamoeba) →
- Sappinia: a single reported case of amoebic encephalitis in a healthy adult, with a brain mass that was removed and survival. Free-living amoeba infections (Naegleria meningoencephalitis, Acanthamoeba) →
Clinical picture
- Unlike Acanthamoeba, it also infects healthy children and adults.
- Most reports come from the Americas, especially Latin America; many Peruvian patients first had a facial plaque.
- Encephalitis: headache, fever, behavior change, focal deficits and seizures; imaging shows several ring-enhancing lesions that can look like tumor, tuberculosis or toxoplasmosis.
Diagnosis
- Biopsy of skin or brain: amoebae (often around vessels) with granulomas; immunofluorescence or immunoperoxidase staining identifies the species.
- PCR and metagenomic sequencing at reference laboratories.
- Cerebrospinal fluid is usually non-specific (lymphocytes, high protein); amoebae are rarely seen there.
- Most cases are diagnosed late or at autopsy.
Treatment
Long multidrug combinations that may include pentamidine, sulfadiazine, flucytosine, a mold-active azole, a macrolide (azithromycin or clarithromycin) and miltefosine; nitroxoline is investigational. Surgery of skin or brain lesions may help. A few survivors had early diagnosis.
Drug class only; doses and regimens are set by the clinician from the current guideline.
In Pharmacology:
Prevention
- Cleaning and covering skin wounds contaminated with soil.
- Biopsy of a non-healing facial plaque in endemic areas.
- Screening of organ donors with unexplained encephalitis.
Test yourself
Think of the answer, then tap the question to see it.
How does Balamuthia mandrillaris enter the body?
Through skin wounds contaminated with soil or by inhalation; then it reaches the brain through the blood.
Which skin lesion can come before Balamuthia encephalitis?
A painless, enlarging plaque on the central face (nose or cheek).
How does Balamuthia differ from Acanthamoeba in the hosts it infects?
Balamuthia also infects healthy children and adults; Acanthamoeba encephalitis is mostly in immunosuppressed people.
What is the best way to confirm the diagnosis?
Tissue biopsy with immunofluorescence or immunoperoxidase staining, or PCR at a reference laboratory.
What makes Sappinia trophozoites distinctive?
They have two nuclei pressed together.
Connections
← Back to the group: Free-living amoebae
Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: CDC - DPDx - Free Living Amebic Infections (CDC, 2024); Balamuthia Infections | Balamuthia Infection | CDC (CDC, 2024); Clinical Care of Balamuthia Infection | Balamuthia Infection | CDC (CDC, 2024).
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Representative model, for educational purposes only.