Contributors:Aileen Lin, MScBMC, David Walker, Jake Ryan, Ahmed A. Abu Ajeene, Katherine May, BSN, RN
Now, let’s review some physiology. Normally, the skin surface is colonized by a huge number of microorganisms that make up the normal skin flora. This flora has a healthy balance that consists mostly of bacteria, such as Staphylococcus epidermidis, as well as low amounts of certain fungi, such as Candida albicans, Malassezia, and dermatophytes like Trichophyton. These microorganisms are typically non-pathogenic, meaning that they don’t cause any disease. In fact, they are beneficial, since they serve as a physical and competitive barrier that helps prevent pathogenic microorganisms from invading and infecting the skin.
Okay, so cutaneous fungal infections are typically caused by a disruption of the healthy balance of the skin flora. Now, clients can develop different infections based on the causative fungus. The most common ones include candidiasis, which is caused by an overgrowth of Candida albicans; as well as tinea or pityriasis versicolor, which is caused by Malassezia furfur; and tinea infections, which are caused by a variety of dermatophyte fungi.
Risk factors of fungal infections include medications like antibiotics or glucocorticoids, poor personal hygiene, as well as warm and humid environments, in addition to close contact with animals, such as dogs, cats, cows, and goats. Additional risk factors include obesity, diabetes mellitus, and being immunocompromised; as well as high estrogen levels due to oral contraceptive use, estrogen therapy, or pregnancy.
So, cutaneous fungal infections occur when the healthy balance of the skin flora gets disrupted, which may allow the fungi in the skin to overgrow. In most cases, a healthy immune system is able to notice and stop this, keeping the fungi under control. However, in some cases, fungi manage to persist, and ultimately cause an infection. Typically, cutaneous fungal infections are superficial and localized; but in certain cases, such as in clients who are severely immunocompromised, fungi may also cause more serious invasive infections, spreading to the bloodstream or to other tissues and organs.
Now, the clinical manifestations of cutaneous fungal infections may vary according to the causative fungus. Candidiasis typically presents as a well-defined erythematous area that’s often itchy, most often involving moist intertriginous areas where two skin surfaces rub together, such as the axillae and groin folds. In babies and young children who wear diapers, Candida infection may cause diaper dermatitis, which presents as a sharp red patch with surrounding or satellite eruptions.
On the other hand, tinea or pityriasis versicolor causes patches of hypo- or hyperpigmentation of the skin, most often involving the neck, chest, back, and arms.
Lastly, tinea infections usually present as an erythematous scaly plaque with a characteristic ring-like appearance; these lesions are sometimes itchy. Now, depending on the body site affected, tinea infections can be classified as tinea capitis when it involves the scalp; tinea barbae when it involves the beard and mustache area, also called barber’s itch; tinea cruris when it involves the groin area, also called jock itch; tinea pedis when it involves the toes or feet, also called athlete’s foot; tinea unguium when it involves the toenails or fingernails, also known as onychomycosis; and finally, tinea corporis when the infection affects any site of the body, excluding the scalp, face or beard, groin, and hands, feet, or nails.
The diagnosis of fungal infections starts with the client's history and physical assessment. This can be followed by microscopic examination of a skin scraping. This scraped sample is put into a potassium hydroxide or KOH solution, which dissolves skin cells while maintaining the fungal cells, making them easier to spot under the microscope. In addition, a Wood’s lamp that emits UV-A light can be used to illuminate and examine the infected skin area. Finally, the diagnosis can also be confirmed with a culture, and some cases may require a tissue biopsy.
Treatment of cutaneous fungal infections typically includes topical antifungal medications, such as ketoconazole, clotrimazole, and miconazole. In clients with candidiasis, topical amphotericin B or nystatin can also be used. Finally, widespread cases may require oral antifungals, such as fluconazole, itraconazole, terbinafine, and griseofulvin; as well as amphotericin B for candidiasis.