Ecology and Mechanism of Infection
The natural reservoir for microorganisms causing subcutaneous mycoses is the environment. These pathogenic and opportunistic fungi freely inhabit soil and wooden surfaces. Furthermore, their favored breeding grounds are decaying and rotting plants, which determines the specific nature of human contact with the agent.
Infection occurs exclusively via a traumatic route. For the fungus to penetrate the body, a portal of entry in the form of microtrauma to the skin is required. The infection is inoculated into tissues during accidental skin damage by splinters, plant thorns, or the entry of any other foreign bodies on whose surface fungal elements are present. Without a breach in the integrity of the epidermis, the development of a subcutaneous mycosis is impossible.
Pathogenesis Features
A key feature of subcutaneous mycoses, distinguishing them from superficial dermatophytoses, lies in the significant depth of tissue involvement. The pathological process is never limited solely to the epidermis.
Fungal invasion steadily spreads deeper, sequentially capturing the deep layers of the dermis and subcutaneous adipose tissue. In the absence of timely arrest of the process, the infection penetrates even deeper, involving the underlying structures of the musculoskeletal system—muscles and fascia—in the inflammation. Such deep damage determines the severity of the clinical course and the complexity of therapy for this group of diseases.
Sporotrichosis and Chromoblastomycosis
In medical microbiology, several main nosological forms of subcutaneous mycoses are distinguished, each associated with specific groups of microorganisms.
- Sporotrichosis. A chronic infectious disease. Its primary and most well-known causative agent is the fungus Sporothrix schenckii.
- Chromoblastomycosis. This form of pathology is caused by specific pigmented fungi. The main representatives of pathogens provoking the development of chromoblastomycosis include microorganisms of the genera Phialophora (specifically the subspecies Fonsecaea), Cladophialophora, Exophiala, and Rhinosporidium.
Mycetoma and Phaeohyphomycosis
In addition to sporotrichosis and chromoblastomycosis, two other nosological forms of subcutaneous mycoses play a significant clinical role:
- Eumycotic mycetoma (maduromycosis). A classic polyetiological disease. Polyetiological means that the clinical picture of mycetoma can be provoked not by a single specific species, but by an entire group of diverse fungi. Among the most frequent causative agents are representatives of the genera Pseudallescheria, Madurella, Acremonium, and Leptosphaeria.
- Phaeohyphomycosis. This pathology is caused by so-called dematiaceous, i.e., darkly pigmented fungi. This extensive group of pathogens includes fungi belonging to the genera Exophiala, Phialophora, Wangiella, Bipolaris, Alternaria, and Cladosporium.