Tropical ulcer: causes, symptoms, diagnosis, and treatment

Tropical ulcer, also known as tropical phagedenic ulcer, is a chronic necrotizing ulcer of the skin and subcutaneous tissue caused simultaneously by various bacteria, accompanied by pain and malodor, often in the calves, mainly in tropical and subtropical regions.


Causes

Fusobacterium, usually Fusobacterium ulcerans, can be isolated from the ulcer and papule in the early stage. Borrelia vincentii or other anaerobic bacteria can also be visible. Other aerobic bacteria such as Staphylococcus aureus can be detected in the advanced ulcer. It is also believed that the disease is caused by a special mycobacterium.

Trauma, malnutrition such as protein deficiency and hypovitaminosis A, anemia, certain chronic diseases, and poor sanitation are the predisposing factors for this disease. The disease has a high incidence in soldiers fighting in the tropical jungles.


Signs and Symptoms

Most ulcers occur in the areas susceptible to trauma, scratches, stab wounds, or insect bites, are more common in calves, feet, and forearms, especially in the lower third of the calves. A small papule or blood blister occurs on the normal skin, evolving quickly into a sharp edged, 2 - 6cm or more in diameter, round or oval ulcer after rupture, with blueish red edges, with mild infiltration, with a cyathiform base covered firmly by greenish gray membrane, with malodorous exudates under the membrane. In the late stage, the muscles, tendons, and bones underneath the membrane may be destroyed. The disease evolves into a chronic disease in several weeks or months, and the ulcer surfaces are pale, fibrotic, and painless. Due to the poor basic nutritional status of patients, the skin lesions heal very slowly, leaving scars after healing. Common complications are erysipelas, lymphangitis, lymphadenitis, and gangrene. In some patients, the ulcer is unhealed in many months, and hyperplasia in the edges is present, eventually progressing to squamous cell carcinoma. In severe cases, the continuous progression of the condition may lead to death.


Histopathology

Biopsy with the ulcer is performed. In microscopy, coagulative necrotic tissue with a large number of bacteria on the surface layer, granulation tissue in the middle layer, and abundant blood vessels in the bottom layer can be seen, and the peripheral epithelioid tissue proliferation is visible.


Diagnosis

Diagnosis relies primarily on rapid progression of the rash, typical clinical manifestations, and endemic prevalence. Although various bacteria such as Fusobacterium and spirochetes are important pathogens, their presence or absence has no diagnostic value, and their isolation and culture are impracticable.


Treatment

For the acute ulcer, debridement should be performed. Wet compress with potassium permanganate solution during the day and topical bacitracin ointment at night are feasible. Procaine penicillin 1,000,000U/day intramuscularly for 7 - 10 days or streptomycin 1g/day intramuscularly for 10 days can be administered. Erythromycin 0.25g orally 4 times a day can also be effective quickly, with little recurrence. Metronidazole is effective in the treatment of acute ulcers, and metronidazole 400mg/day can relieve pain and eliminate the secretion of malodor within 24 hours.

Systemic antibiotics are less effective in the treatment of the chronic ulcer. Skin grafting is feasible for the persistent ulcer. When deep tissues and bones are invaded, surgical resection should be performed, and large ulcers may require skin grafting.