Mycetoma

Synonyms

Madura foot.

Epidemiology

The so-called ‘mycetoma belt’ (latitude 15°S and 30°N). It is endemic in Sudan, Somalia, Senegal, India, Yemen, Mexico and Venezuela, and affects preferentially farmers and poor populations in remote areas with higher humidity.

Males are more frequently affected than females (4:1). Age range: 30-40 years.

Definition

Chronic granulomatous infection of the skin and subcutaneous tissue, either by fungi (60%; eumycetoma) or by bacteria (40%; actinomycetoma).

Aetiology & Pathogenesis

Causative agents of eumycetoma: Madurella mycetomatis, (most common), Madurella grisea, Pseudoallescheria boydii, Leptosphaeria senegalensis.
Causative agents of actinomycetoma: Nocardia spp., including Nocardia brasiliensis, Nocardia asteroids, and Nocardia otidiscaviarum.

Signs & Symptoms

The clinical presentation of eumycetoma and actinomycetoma are almost identical. They involve the skin and subcutaneous tissue, presenting the classic triad of hard woody swelling, painless discharging sinuses and presence of grains (colonies of bacteria or fungi).

Variants:

Swelling without sinuses.
Cystic type.
Verrucous plaque type.

Localisation

Mostly foot, but also any other part of the body.

Classification

See aetiopathology and symptoms.

Laboratory & other workups

KOH

Fungal hyphae: periodic-acid–Schiff, Gomori methanamine silver stain.
Nocardia species: gram-positive and weakly acid-fast-positive. Actinomadura grains are Gram-positive and acid-fast-negative.

Ultrasound and radiograph, Magnetic resonance imaging (MRI).

PCR and grain cultures.

Dermatopathology

Chronic fibrosing inflammation with suppurative granuloma and mycetoma grains. Periodicacid–Schiff (PAS), Gomori methenamine silver (GMS) and gram stains.

Course

Chronic; untreated, the infection spreads through the fasciae and may involve bone and muscle.

Complications

Socioeconomic burden.

Invasion of the periosteum and adjacent bones, leading to osteomyelitis.

Vertebral compression with neurological manifestations when affecting the back.

Rarely lymphatic spread.

Diagnosis

Clinically, histologically, investigation of grains.

Ultrasound and radiograph, Magnetic resonance imaging (MRI) for recognizing the extension of the disease.

Differential diagnosis

Actinomycosis; aspergillosis; botryomycosis; chromoblstomycosis; coccidioidomycosis; sporotrichosis; tuberculosis; osteomyelitis; neoplasias, podoconisis.

Prevention & Therapy

Surgical treatment is indicated for small, localized lesions and also for large lesions to reduce the organism load. eumycetoma requires a combination of antifungals and surgery and may still have recurrences.

Actinomycetoma responds well to antibiotic treatment: Amikacin 15 mg/kg IM divided into two doses + sulfamethoxazole (35 mg/kg/day) and trimethoprim (7 mg/kg/day) divided into three doses for 21 days.
Eumycetoma requires a combination of antifungals and surgery and tends to recurre: ketoconazole (400 mg/day), itraconazole (200–400 mg/day), Posaconazole, (200 mg four times daily), voriconazole 400–600 mg/day, amphotericin B (0.5–1.25 mg/kg per day) and terbinafine (500–1000 mg/day), alone or in any combination.

Special

Note: fungal and bacterial mycetoma respectively need completely different therapeutic approaches.

10.2.3 Mycetoma