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Cutaneous Mycoses

What Are They, Causes, Treatment, and More

Author: Anna Hernández, MD

Editors: Ahaana Singh, Kelsey LaFayette, BAN, RN

Illustrator: Jillian Dunbar

Copyeditor: Joy Mapes

What are cutaneous mycoses?

Cutaneous mycoses are a group of superficial fungal infections affecting the skin and its appendages, including the hair and nails. The term mycoses generally refers to an infection caused by fungi, also known as mycetes, while cutaneous refers to the involvement of the skin. 

Fungi are a diverse group of living organisms that can be found nearly everywhere: in the environment, parasitizing animals and plants; in the soil; and on and inside the human body. Normally, the fungi that live on the skin’s surface are relatively harmless, but in certain cases, they may grow out of control or penetrate the skin through a wound, causing an infection.

Since fungi thrive in warm, moist environments, cutaneous mycoses are more likely to affect the feet, groin, armpits, and other skin folds -- body areas that are favorable for fungal growth. Additionally, certain environmental conditions (e.g., warm and humid climates, crowded places, communal showers, locker rooms) can provide an excellent breeding ground for the growth and spread of many fungal diseases. 

What are the different types of mycoses?

Mycoses, or fungal infections, can be broadly classified as superficial, cutaneous, subcutaneous, and systemic, based on their degree of invasiveness. 

Superficial and cutaneous mycoses are both caused by fungi that affect the superficial layers of skin, hair, and nails. The main difference between them is that superficial mycoses cause little or no inflammation, whereas cutaneous mycoses generally trigger an inflammatory response that causes skin redness and itching. 

Subcutaneous mycoses are localized infections of the skin and underlying tissue that usually result from a cut or puncture wound to the skin (e.g., from a rose thorn). The opening in the skin allows fungi from the environment to enter the skin and gain access to deeper tissues. 

Finally, systemic mycoses affect internal organs (e.g., lungs, brain, gastrointestinal tract) and are generally caused by opportunistic fungi. These microbes are typically harmless for healthy individuals, but they can take advantage of an opportunity, like a weakened immune system, to cause an infection. 

What causes cutaneous mycoses?

There are several types of fungal infections of the skin. Most cutaneous mycoses are caused by dermatophytes, a group of filamentous fungi that colonize and infect keratinized tissues, including the outermost layer of skin (i.e., stratum corneum), hair, and nails. Dermatophytes are commonly found in the environment and are spread from one person to another through direct skin contact or, more rarely, through contact with an infected animal or soil. Although there are a number of dermatophyte species, most dermatophyte infections are caused by fungi of the Trichophyton, Microsporum, and Epidermophyton genera. 

Dermatophyte infections of the skin are also called tineas, or ringworm, due to the ring-like appearance of the skin lesions they typically produce. Some tineas have distinctive names descriptive of the affected body part. For instance, tinea corporis (i.e., ringworm) affects the arms, trunk, and legs; tinea capitis (i.e., scalp ringworm) affects the scalp and hair shafts; tinea cruris (i.e., jock itch) affects the groin area and inner thighs; and tinea pedis (i.e., athlete’s foot) affects the feet. 

In addition to dermatophytes, cutaneous mycoses may also be caused by yeasts of the Candida genus. Candida is naturally present on the skin and mucous membranes. When the amount of Candida is low, it is harmless, but when it starts to overgrow, it can damage the skin and nearby tissues, resulting in a superficial skin infection. A weakened immune system is often the reason for Candida overgrowth. As a result, candidiasis typically affects individuals with immunosuppressive conditions (e.g., diabetes, HIV infection), who are more vulnerable to opportunistic infections.

More rarely, cutaneous mycoses can be due to infection by non-dermatophytic fungi, like an Aspergillus species. Aspergillus is a family of molds consisting of many different species, some of which can cause a condition known as aspergillosis. Cutaneous aspergillosis is a rare form of locally invasive disease that typically occurs when invasive aspergillosis spreads to the skin from somewhere else in the body, such as the lungs. Primary infection of the skin --such as after a surgery, trauma, or burn wound -- may also occur but is much less common.

What are the signs and symptoms of cutaneous mycoses?

Signs and symptoms of cutaneous mycoses vary depending on the infectious agent, location of the infection, and severity of the infection. 

Tinea infections often present with an itchy rash that has a central clearing surrounded by an inflamed, scaly border. Also called ringworm, these lesions have their characteristic ring-like appearance because they tend to grow in an outward pattern. Despite their characteristic appearance, tineas may still be hard to distinguish from other cutaneous mycoses, including Candida infections. 

Cutaneous candidiasis often presents as red skin patches with small satellite lesions that usually affect skinfold areas (e.g., armpits, groin, under the breasts). Candida can also affect the nails, causing them to harden and turn yellow. 

Finally, cutaneous aspergillosis can present with distinctive skin wounds, known as eschars, in the affected area.

How are cutaneous mycoses diagnosed and treated?

Many cutaneous mycoses can be diagnosed by their clinical appearance upon physical examination. However, if the diagnosis is unclear, it may be confirmed with additional diagnostic tests, including direct microscopy, fungal cultures, or Wood’s lamp examination. 

Microscopic observation of skin scrapings, hair, or nails, is often performed to detect the presence of fungi. The samples are usually prepared with a potassium hydroxide (KOH) solution that dissolves the keratin found in tissues, so the branching filaments of the fungi (hyphae) or fungal spores can be seen under the microscope. In individuals who do not respond well to initial treatment, the specimens may be grown on a Sabouraud dextrose agar plate, a growth medium that supports fungal growth while limiting the growth of most bacteria. Finally, Wood’s lamp examination uses an ultraviolet light to detect areas of fluorescence that may be caused by certain types of fungi. 

Treatment of cutaneous mycoses varies depending on the underlying cause of infection. In general, most cutaneous mycoses require treatment with antifungal medications (e.g., azole antifungals, amphotericin, terbinafine). Antifungal medications may be topical or oral, and the type recommended generally depends on the severity of the infection. Additional measures that can help prevent repeated fungal infections include following treatment recommendations closely, practicing good hygiene, wearing clothing that allows air circulation next to the skin, and keeping the skin clean and dry. 

What are the most important facts to know about cutaneous mycoses?

Cutaneous mycoses are a group of superficial fungal infections affecting the skin, hair, and nails. They may be caused by different kinds of fungi, including dermatophytes, yeasts of the Candida genus, and other non-dermatophytic fungi. Signs and symptoms depend on the specific fungal infection. For instance, dermatophyte infections (tineas) present with itchy, ring-like lesions at the site of infection, while cutaneous candidiasis can present with a localized rash in skinfold areas. Diagnosis of cutaneous mycoses is often suspected upon clinical examination of the lesions, and it can be confirmed with additional tests, including direct microscopy, fungal cultures, and Wood’s lamp examination. An individual may reduce their susceptibility to mycoses by practicing good hygiene, wearing clothing that allows air circulation next to the skin, and keeping the skin clean and dry. Treatment generally requires topical or oral antifungal medications. 

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