Subcutaneous Mycoses Overview

Subcutaneous Mycoses

• Include diseases involving under skin tissues: Mycetoma, Sporotrichosis, Chromoblastomycosis.

Mycetoma (Madura Foot)

• Clinical syndrome characterized by localized, deforming, swollen lesions and exudative abscesses.
• Affects cutaneous and subcutaneous tissues and can involve bone.
• Caused by a combination of Actinobacteria and fungi.

Actinobacteria

• Filamentous bacteria associated with mycetoma include:
  • Actinomyces israelii (normal flora)
  • Actinomadura madurae
  • Nocardia species (N. asteroides, N. otitidis-caviarum, N. brasiliensis)
  • Streptomyces somaliensis
• Most exist in soil and plants except A. israelii.

Fungi

• Key fungi involved in mycetoma:
  • Pseudallescheria boydii
  • Madurella mycetomatis
  • Madurella grisea
  • Aspergillus species
  • Acremonium species
  • Fusarium species
• Primarily found in soil and plants.

Environmental Niches

• Commonly found in soil, plants, and certain devices.

Etiological Types of Mycetoma

• Actinomycotic Mycetoma: Caused by Actinobacteria.
• Eumycotic Mycetoma: Caused by fungi.

Mode of Transmission

• Transmission occurs through cutaneous inoculation after trauma (e.g., pin, thorn, thistle injuries).

Ecology and Epidemiology

• Distributed worldwide; higher frequency in tropical regions (e.g., India, Sudan, Mexico) and lower in subtropical areas (e.g., Iran).
• Affects all age groups, with a higher incidence in males, especially in farming and gardening occupations.

Clinical Manifestations

• Long incubation period (6 months to 10 years).
• Presenting symptoms include:
  • Tense nodules and abscesses with multiple sinus tracts.
  • Granules may be produced, varying in size and color.
  • Edema, disfigurement, and potential metastasis to joints or bone (not nerves/muscles).

Anatomic Sites of Infection

• Pedal mycetoma: Lesions localized to the foot.
• Extrapedal mycetoma: Involvement in areas such as the leg, trunk, or arm.

Laboratorial Diagnosis

• Sample pus, exudate, or granules for analysis.
• Smearing with KOH or PAS staining highlights:
  • Actinomycotic grains (branched filaments) versus Eumycotic grains (septate mycelia).
• Culturing on selective media (S, Sc, BHI).

Treatment

• Eumycotic Mycetoma: Amphotricine-B, Itraconazole.
• Actinomycotic Mycetoma: Dapsone combined with Streptomycin.

Sporotrichosis (Rose Syndrome)

• Caused by the dimorphic fungus Sporothrix schenckii, typically found in soil and plants.

Mode of Transmission

• Common injuries facilitating transmission include:
  • Pin, thorn, thistle trauma, and bites from animals (dogs, parrots, cats).

Epidemiology

• Endemic in tropical areas (Mexico and Brazil), sporadic in subtropical regions (Iran).
• Affects all ages, with a higher frequency among males due to occupational exposure.

Clinical Types

• Fixed cutaneous sporotrichosis: Single painless lesions without lymphatic involvement.
• Lymphocutaneous sporotrichosis: Subcutaneous nodules and ulcerative lesions with lymphadenopathy.
• Muco cutaneous sporotrichosis: Rare with involvement in oral and nasal areas.
• Extra cutaneous sporotrichosis: Dissemination to bones, eyes, and lungs, typically after prior skin lesions.

Laboratorial Diagnosis

• Sampling of pus, exudates, or biopsy materials.
• Direct smears reveal yeast bodies, asteroid bodies; cultures differ based on temperature.

Treatment

• Iodine solutions (oral and injectable), Amphotricine-B, Imidazoles.

Chromoblastomycosis

• A subcutaneous infection leading to verrucoid, compact lesions caused by dematiaceous fungi such as Fonsecae and Cladosporium species.

Clinical Manifestation

• Papules and nodules that can develop into verrucoid lesions.

Laboratorial Diagnosis

• Direct examination via smear with KOH shows sclerotic bodies.
• Cultures reveal dark mycelia and pigmented spores.

Treatment

• Amphotricine-B, Imidazoles.