Introduction
Subcutaneous mycoses are a type of fungal infection that affects the subcutaneous tissues, which are the layers of tissue that lie beneath the skin. This type of fungal infection is caused by a group of fungi known as the dematiaceous fungi, which are characterized by dark pigmentation in their cell walls.
Subcutaneous mycosis can occur in both humans and animals and is typically acquired through traumatic inoculation of the fungal spores into the skin. This can occur as a result of exposure to contaminated soil or vegetation, or through contact with an infected animal or human.
Also, read what is mycosis
Type of subcutaneous mycosis
Chromoblastomycosis:
Chromoblastomycosis is a chronic fungal infection caused by several different species of fungi, including Fonsecaea pedrosoi, Cladosporium carrionii, and Phialophora verrucosa. The infection typically begins as a small nodule or papule on the skin, which gradually enlarges and becomes wart-like in appearance. Over time, the lesion can become chronic, and may spread to involve deeper tissues, such as the lymphatic system.
Causes and risk factors
Chromoblastomycosis is primarily a disease in tropical and subtropical regions. It is typically acquired through traumatic inoculation of the fungal spores into the skin, often due to exposure to contaminated soil or vegetation. Other risk factors include living or working in rural areas and having a weakened immune system.
Clinical presentation and symptoms
The characteristic clinical feature of chromoblastomycosis is the formation of wart-like lesions on the skin. These lesions are often accompanied by itching, pain, and discomfort. As the infection progresses, the lesion may become larger and more extensive and may involve deeper tissues, such as the lymphatic system. In severe cases, the infection may lead to tissue damage and loss.
Diagnosis and treatment options
Diagnosis of chromoblastomycosis is typically based on a combination of clinical evaluation, laboratory tests, and imaging studies. Laboratory tests may include direct microscopy, culture, and molecular methods to identify the specific type of fungus causing the infection. Treatment of chromoblastomycosis typically involves a combination of antifungal therapy and surgery. Antifungal therapy may include the use of topical or systemic antifungal drugs, depending on the type and severity of the infection. Surgery may be necessary to remove infected tissue or to drain abscesses or nodules.
Mycetoma
Mycetoma is a chronic fungal infection caused by several different types of fungi and bacteria. The infection typically begins as a small nodule or tumor in the subcutaneous tissues, which gradually enlarges and becomes more extensive over time. The infection can cause swelling, deformity, and loss of function in the affected area.
Causes and risk factors
Mycetoma can be caused by a variety of bacteria and fungi, including Actinomycetes, Nocardia, and fungi from the genera Madurella, Pseudallescheria, and Exophiala. These organisms typically enter the body through skin trauma or wounds, and can spread to deeper tissues over time. The exact risk factors for mycetoma are not well understood, but it is more common in people who live in rural or tropical areas, where exposure to soil and vegetation is high.
Clinical presentation and symptoms
The clinical presentation of mycetoma can vary depending on the causative organism, but typically involves the formation of firm, painless nodules or abscesses in the subcutaneous tissue. The nodules may be accompanied by draining sinuses or fistulas that discharge a purulent material. The overlying skin may be discolored or thickened, and the affected area may become swollen and tender over time. In advanced cases, mycetoma can lead to bone destruction and deformity, particularly in the hands and feet.
Diagnosis
The diagnosis of mycetoma is typically made based on a combination of clinical and laboratory findings. A healthcare provider may perform a physical examination to assess the extent of the infection and take a sample of the discharge for laboratory analysis. Laboratory tests may include culture and microscopy of the discharge, as well as imaging studies such as X-rays, CT scans, or MRI scans to evaluate the extent of tissue involvement.
Treatment options
The treatment of mycetoma typically involves a combination of antifungal or antibiotic therapy and surgical intervention. The specific treatment plan will depend on the causative organism and the extent of tissue involvement.
- Antifungal therapy: Antifungal therapy may be prescribed for several months or even years, depending on the severity of the infection. The choice of drug will depend on the causative organism. It may include agents such as itraconazole, voriconazole, or amphotericin B for fungal mycetoma, and sulfonamides or aminoglycosides for bacterial mycetoma.
- Surgery: Surgery may be necessary to remove the infected tissue and promote healing. The type of surgery will depend on the extent of tissue involvement and may include excision, debridement, or amputation. In some cases, a combination of surgical and medical therapy may be necessary to achieve a successful outcome.
Sporotrichosis
Sporotrichosis is a chronic fungal infection caused by the Sporothrix schenckii fungus. It is a rare infection that typically affects the skin, but can also involve other organs such as the lungs or bones.
Causes and risk factors
The Sporothrix schenckii fungus is typically found in soil, plants, and decaying organic matter, and can enter the body through small cuts or puncture wounds. Sporotrichosis is more common in people who work with soil, plants, or animals, such as gardeners, farmers, and veterinarians. It can also occur in people with weakened immune systems, such as those with HIV/AIDS or cancer.
Clinical presentation and symptoms
Sporotrichosis typically starts as a small, painless bump or nodule at the site of infection, which may gradually spread to nearby lymph nodes and form a chain of nodules. The nodules may be accompanied by ulcers, blisters, or draining sinuses, and can be itchy or tender. In some cases, the infection can spread to other parts of the body, including the lungs, bones, or central nervous system, which can result in more serious symptoms such as fever, cough, or neurological deficits.
Diagnosis
The diagnosis of sporotrichosis is typically made based on a combination of clinical and laboratory findings. A healthcare provider may perform a physical examination to assess the extent of the infection and take a sample of the discharge for laboratory analysis. Laboratory tests may include culture and microscopy of the discharge, as well as imaging studies such as X-rays, CT scans, or MRI scans to evaluate the extent of tissue involvement.
Treatment options
The treatment of sporotrichosis typically involves a combination of antifungal therapy and surgical intervention, depending on the extent and severity of the infection.
- Antifungal therapy: Antifungal drugs such as itraconazole, fluconazole, or terbinafine may be prescribed for several months or even years, depending on the severity of the infection. The specific drug and duration of therapy will depend on the location and extent of the infection, as well as the patient’s overall health status.
- Surgery: Surgery may be necessary to remove the infected tissue and promote healing, particularly in cases where the infection has spread to deeper tissues or bone. The type of surgery will depend on the extent of tissue involvement and may include excision, debridement, or amputation.
Phaeohyphomycosis
Phaeohyphomycosis is a fungal infection caused by a group of pigmented fungi known as dematiaceous fungi. These fungi are found in the soil, water, and decaying plant matter. Phaeohyphomycosis can affect various organs in the body, including the skin, eyes, sinuses, lungs, brain, and bones.
Causes and risk factors
The main risk factor for phaeohyphomycosis is exposure to dematiaceous fungi. The fungi can enter the body through the inhalation of spores, inoculation through the skin or mucous membranes, or ingestion of contaminated food or water. People with weakened immune systems, such as those with HIV/AIDS, cancer, or organ transplants, are at higher risk of developing the infection.
Clinical presentation and symptoms
The symptoms of phaeohyphomycosis depend on the location and severity of the infection. In cases of skin infection, patients may present with nodules, abscesses, or ulcers that may be painful, itchy, or discharging pus. In cases of pulmonary infection, patients may present with cough, fever, chest pain, or difficulty breathing. In cases of central nervous system infection, patients may present with headache, seizure, or altered mental status.
Diagnosis
The diagnosis of phaeohyphomycosis is based on a combination of clinical and laboratory findings. Laboratory tests may include culture and microscopy of the infected tissue or fluid, as well as imaging studies such as X-rays, CT scans, or MRI scans to evaluate the extent of tissue involvement. Molecular methods such as polymerase chain reaction (PCR) may also be used to identify specific fungal species.
Treatment options
The treatment of phaeohyphomycosis typically involves a combination of antifungal therapy and surgical intervention, depending on the extent and severity of the infection.
- Antifungal therapy: Antifungal drugs such as itraconazole, voriconazole, or posaconazole may be prescribed for several months or even years, depending on the severity of the infection. The specific drug and duration of therapy will depend on the location and extent of the infection, as well as the patient’s overall health status.
- Surgery: Surgery may be necessary to remove the infected tissue and promote healing, particularly in cases where the infection has spread to deeper tissues or bone. The type of surgery will depend on the extent of tissue involvement and may include excision, debridement, or amputation.
Subcutaneous zygomycosis
Subcutaneous zygomycosis, also known as entomophthoramycosis, is a rare fungal infection caused by fungi belonging to the order Entomophthorales. These fungi are found in soil and decaying plant matter and can enter the body through skin wounds or insect bites.
Causes and risk factors:
The main risk factors for subcutaneous zygomycosis are exposure to the fungi and a weakened immune system. People with diabetes, cancer, or HIV/AIDS are at higher risk of developing the infection. Other risk factors include poor hygiene, exposure to contaminated soil or vegetation, and the use of immunosuppressive medications.
Clinical presentation and symptoms
The symptoms of subcutaneous zygomycosis depend on the location and extent of the infection. In most cases, the infection begins as a painless nodule or swelling at the site of skin injury or insect bite. The nodule may gradually increase in size and become red, tender, and hard. As the infection spreads, it may cause tissue necrosis and form draining sinuses or ulcers. In some cases, the infection may spread to deeper tissues or bones, causing more serious complications.
Diagnosis
The diagnosis of subcutaneous zygomycosis is based on a combination of clinical and laboratory findings. Laboratory tests may include culture and microscopy of the infected tissue or fluid, as well as imaging studies such as X-rays, CT scans, or MRI scans to evaluate the extent of tissue involvement. Molecular methods such as PCR may also be used to identify the specific fungal species.
Treatment options
The treatment of subcutaneous zygomycosis typically involves a combination of antifungal therapy and surgical intervention, depending on the extent and severity of the infection.
Antifungal therapy: Antifungal drugs such as amphotericin B, posaconazole, or itraconazole may be prescribed for several months, depending on the severity of the infection. The specific drug and duration of therapy will depend on the location and extent of the infection, as well as the patient’s overall health status.
Surgery: Surgery may be necessary to remove the infected tissue and promote healing, particularly in cases where the infection has spread to deeper tissues or bone. The type of surgery will depend on the extent of tissue involvement and may include excision, debridement, or amputation.
| Disease | Causative organisms |
| Sporotrichosis | Sporothrix spp. |
| Chromoblastomycosis | Fonsecaea, Phialophora, Cladophialophora etc. |
| Phaeohyphomycosis | Cladophialophora, Exophiala,Curvularia, Exserohilum etc |
| Mycotic mycetoma | Scedosporium, Madurella, Trematosphaeria,Acremonium, Exophiala etc. |
| Subcutaneous zygomycosis(Entomophthoromycosis) | Basidiobolus ranarumConidiobolus coronatus |
Laboratory tests for Identification
Laboratory tests are an important component of the diagnostic workup for subcutaneous mycosis. These tests may include:
- Direct microscopy: A sample of tissue or fluid from the affected area is examined under a microscope to look for fungal elements, such as hyphae or spores.
- Culture: A sample of tissue or fluid from the affected area is cultured in the laboratory to grow and identify the specific type of fungus causing the infection.
- Molecular methods: These tests use techniques such as polymerase chain reaction (PCR) to detect and identify the specific DNA of the fungus causing the infection.
Imaging studies
Imaging studies such as X-rays, CT scans, and MRI scans may be used to evaluate the extent of the infection and to assess for any underlying tissue damage or complications. For example, in cases of mycetoma, imaging studies may be used to identify any bone involvement or to assess the size and location of the abscesses.
In some cases, a skin biopsy may be necessary to confirm the diagnosis of subcutaneous mycosis. During a biopsy, a small sample of tissue from the affected area is removed and examined under a microscope to look for signs of fungal infection.
Conclusion
In conclusion, subcutaneous mycosis remains a challenging group of infections that requires a multidisciplinary approach to management. Advances in diagnosis and treatment have improved outcomes, but further research is needed to better understand these infections and to develop new strategies for prevention and treatment. With continued research, it is hoped that better options for prevention, diagnosis and treatment of subcutaneous mycosis will be available in the future.
References
- Mishra, K., Das, S., Goyal, S., Gupta, C., Rai, G., Ansari, M. A., … & Singal, A. (2014). Subcutaneous mycoses caused by Rhytidhysteron species in an immunocompetent patient. Medical Mycology Case Reports, 5, 32-34.
- https://www.id.theclinics.com/article/S0891-5520(02)00066-1/fulltext
- https://www.adelaide.edu.au/mycology/mycoses/subcutaneous-mycoses
