Examination of the skin and its components (nails and hair) for the presence of fungi involves direct microscopic observation of the specimen, the microbiological culture of the specimen, and identification of the fungus in the event of a positive result.
Fungal infections of keratinized tissues (skin, hair, and nails) can be caused by dermatophytes belonging to the genus Epidermophyton, Microsporum, and Trichophyton. Opportunistic skin infections that resemble those caused by dermatophytes can be caused by yeasts or other fungi that are usually saprophytes.
Dermatophytes
Dermatophytes are fungi that can be divided into three groups: Anthropophilic, Zoophilic, and Geophilic. Anthropophilic dermatophytes are transmitted from person to person and are the most common infections. Zoophilic skin infections are usually sporadic. Infections with geophilic dermatophytes are more common after contact with the soil or through an infected animal after contact with the soil. The diagnosis is made by observing the presence of fungal hyphae on the skin, hair, or nails. However, it is important to cultivate the material in order to determine the genus and species of the fungus in order to ensure that the most appropriate treatment is selected.
Dermatophyte infections (also known as tinea) are commonly referred to as tinea followed by the Latin name of the area of the body involved. The most common skin infections in adults are tinea pedis (athlete's foot) which can also include tinea unguium (onychomycosis) and in children tinea captis (fungal infection of the scalp).
Dermatophyte infection is cutaneous and is generally confined to non-live keratinized layers in patients who are immunologically sufficient. This is because dermatophytes cannot penetrate tissues that are not fully keratinized (that is, deeper tissues and organs). However, reactions to such infections can range from mild to severe depending on the host's immune response, fungal infectivity, site of infection, and certain environmental factors. The group of dermatophytes is classified into three genera: Epidermophyton, Microsporum, and Trichophyton.
Non-Dermatophyte Fungi
There are some non-dermatophyte fungal species that can infect healthy skin and include Scytalidium dimidiatum, Scytalidium hyalinum, Phaeoannellomyces werneckii, and Piedraia hortae. Non-dermatophyte species, including those mentioned above, can infect nails that have been damaged by injuries, other diseases, or pre-existing infection by dermatophytes. Non-dermatophyte fungi are responsible for less than 5% of onychomycoses. From Candida species, Candida parapsilosis, Candida guilliermondii, and Candida albicans have been reported as important causes of onychomycosis.
The skin may be a target organ for the development of metastatic, possibly blood-borne infections from a variety of fungi that cause systemic fungi in immunosuppressed patients (filamentous fungi such as Aspergillus and Fusarium species, Candida species, Cryptococcus neoformans, etc). Occasionally, fungi such as Sporothrix schenckii or Cryptococcus neoformans can penetrate the tissues through transdermal inoculation and subsequently cause local, or possibly even systemic, disease. Cryptococcosis in patients with kidney transplantation and HIV infection may occur with skin lesions.
Also, skin lesions can be contaminated by Aspergillus and Alternaria fungi as well as species of Zygomycetes. In most cases, fungal growth is only local, but it can cause extensive tissue necrosis.
Clinical manifestations of superficial fungal infections
Tinea barbae
The infection of the beard can be mild to severe hair folliculitis which may resemble Staphylococcus aureus infection. Tinea barbae is often associated with zoophilic dermatophytes such as Trichophyton verrucosum, Trichophyton mentagrophytes var. mentagrophytes, and rarely Trichophyton mentagrophytes var. erinacei. Sometimes it can be due to the anthropophilic Trichophyton rubrum.
Tinea capitis
Infection of the scalp is usually caused by species of the genus Trichophyton or Microsporum. Infection can range from mild lesions to highly inflammatory reactions with folliculitis, scarring, and alopecia. The surface of the skin and the hair can also be involved. The arrangement of the fungal spores on the hair stem may be diagnostic as to the species of fungus.
Tinea corporis
This infection can include the skin of the torso, shoulders, and limbs. The infection can range from mild to severe and is usually presented as annular scaly lesions with clear, elevated, and erythematous borders.
Tinea cruris
Infections in the groin area, perineum, and perianal area are more common in adult men. Trichophyton rubrum and Epidermophyton floccosum are the most common fungal species isolated from these lesions. The lesions are erythematous to brown and are covered by fine, dry scales. The lesions may extend downward to the inner side of the thigh and have elevated, defined borders that may have small vesicles.
Tinea favosa
This is a serious and chronic condition that is more common in Africa and Asia. This condition is usually caused by Trichophyton schoenleinii.
Tinea imbricata
It is a chronic infection, which is a manifestation of tinea corporis and is found mainly in islands of the Pacific Ocean. It has a very distinctive appearance with concentric rings of overlapping scales. The only known causative agent is Trichophyton concentricum.
Tinea manuum
The palms of the hands and the interdigital areas are affected. This condition is commonly referred to as diffuse hyperkeratosis and is most often caused by Trichophyton rubrum as well as other species of Trichophyton and Microsporum.
Tinea pedis (Athlete's foot)
Toes and soles are most often affected. In particular, the areas between the fourth and fifth toes may show moisture, scaling, and cracks in the skin. Another form is the chronic, slender, hyperkeratotic type with thin gray scales covering the areas of the soles, heels, and lateral parts of the foot. The most common agents of tinea pedis are Trichophyton rubrum, Trichophyton mentagrophytes var. interdigital and Epidermophyton floccosum.
Tinea unguium (Onychomycosis)
The term onychomycosis is accepted as a general term for any fungal infection of the nail (from Dermatophytes and Non-dermatophytes).
Tinea versicolor
It is an infection of the keratin layer of the skin with Malassezia furfur fungi. There is little tissue involvement and the disease mainly causes aesthetic changes in the color of the skin. In general, the diagnosis is made by clinical appearance as well as microscopic detection of fungi.
At Diagnostiki Athinon, we perform tests with molecular analyses to identify fungi as pathogenic agents, using various biological materials. New-generation molecular tests are characterized by sensitivity, specificity, accuracy, and speed in the search for pathogenic microorganisms:
Important Note
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. The correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings, and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.
