Buruli ulcer (BU) is a debilitating skin infection caused by the slow-growing bacterium Mycobacterium ulcerans. Classified by the World Health Organization as a neglected tropical disease, BU is primarily found in tropical and subtropical climates, especially in rural West and Central Africa. The extensive tissue damage is caused by mycolactone, a powerful toxin produced by the bacteria. Mycolactone possesses cytotoxic and immunosuppressive properties, allowing the infection to progress without the body’s typical inflammatory response. Understanding the stages of the disease is important for timely diagnosis and management.
Initial and Pre-Ulcerative Presentations
The disease begins subtly in a pre-ulcerative stage that often goes unnoticed, delaying medical attention. This initial presentation takes three main forms: a nodule, a plaque, or edema. A nodule is a firm, painless lump beneath the skin, typically measuring one to two centimeters in diameter.
A plaque is a firm, flattened, and slightly raised area on the skin, which is generally nontender to the touch. Edema is a diffuse, painless swelling that can rapidly involve an entire limb. This variant, seen frequently in Australia, is sometimes misdiagnosed as cellulitis due to the extensive swelling.
A defining feature of all early lesions is the lack of pain or tenderness, resulting from the mycolactone toxin’s analgesic effect. The absence of typical infection signs, such as fever or localized warmth, prevents patients from seeking treatment until the disease progresses. Approximately 90% of lesions occur on the limbs, with lower extremities affected twice as often as the upper limbs.
Characteristics of the Active Ulcerative Stage
If initial lesions are untreated, they progress to the active ulcerative stage. The mycolactone toxin causes extensive tissue necrosis beneath the skin, leading the overlying tissue to break down and slough away, resulting in a characteristic deep open wound.
The ulcer typically appears as a large, crater-like lesion with severely undermined edges, where the skin border hangs over the necrotic base. The base often contains a white or yellowish, cotton-wool-like slough of dead subcutaneous tissue. Tissue destruction can be extensive, sometimes involving up to 15% of the patient’s skin surface.
The toxin’s immunosuppressive action prevents the body from launching an effective defense, allowing bacteria to multiply in the necrotic tissue. This suppression is why systemic symptoms like fever or lymphadenopathy are rare, even with large, destructive wounds. The World Health Organization classifies lesions by size: Category I are small ulcers less than five centimeters, while Category III includes extensive lesions larger than 15 centimeters or those with severe complications.
Essential Strategies for Management and Treatment
Management relies on a combination of specific antibiotics, which has significantly reduced the need for extensive surgery. The standard protocol involves a dual-antibiotic regimen administered daily for eight weeks. The most common combination pairs rifampicin with an injectable aminoglycoside, such as streptomycin or amikacin.
An effective all-oral alternative is rifampicin combined with clarithromycin, often preferred for ease of administration. Antibiotic therapy eliminates M. ulcerans and is often sufficient to heal small lesions completely without surgical intervention. Antibiotics also help reverse the immunosuppression caused by the mycolactone toxin.
For larger or more advanced ulcers, surgery is a necessary component of the treatment plan. This includes debridement, which is the careful removal of dead tissue from the ulcer base to promote healing. Skin grafting may be required to cover large open defects once the wound is clean.
Conservative surgery, like debridement and grafting, is typically performed after several weeks of antibiotic treatment to ensure bacteria are eliminated. Supportive care, including daily wound dressings and pain management, is also an important part of the overall strategy. Early mobilization and positioning of the affected limb are initiated right away to prevent later disability.
Long-Term Outcomes and Functional Limitations
Following treatment and wound closure, the final stage involves the formation of scars, which can be a source of long-term morbidity. The extensive tissue destruction and subsequent healing process often result in large, disfiguring scars, especially problematic when the lesion was located near a joint.
The most severe long-term functional consequence is the development of contractures. These are the permanent tightening of muscles, tendons, or skin that severely limits the range of motion of a joint. Contractures are common, especially at the knee, ankle, elbow, and wrist, resulting in physical disability that can affect a patient’s ability to work or attend school. In some endemic areas, up to 25% of patients with healed lesions experience disability.
Physiotherapy must be an integral part of the long-term care plan, focusing on exercises and splinting to maintain joint mobility and counteract the scar’s tendency to shorten. For severe contractures, reconstructive surgery is often necessary to release the tightened tissue and restore function. Scar management, including compression therapy and massage, is continued for up to two years to prevent hypertrophic scarring and minimize functional limitations.