Fungal Skin Infections

A majority of fungal infections are cutaneous, i.e. affecting only the upper layers of the skin without causing severe illness. Primary etiological agents are Candida fungi, Malassezia furfur and dermatophytic molds from the genera Trichophyton, Microsporumand Epidermophyton.

For many years infections caused by fungi were regarded more as a nuisance rather than life-threatening; nevertheless, when fungal infections become systemic (spreading throughout the body), life-threatening conditions can arise. The usual approach to the treatment of fungal skin infections are topical agents, although oral antifungal agents are sometimes used.

Candidiasis of the skin

Candida is a genus of non-photosynthetic fungi that are common causes of infections in humans; among them, Candida albicans is most commonly encountered. Acute oral candidiasis is seldom observed in health adults, but may appear in up to 5% of newborns and 10% of the elderly, manifesting with white patches on the surface of the labial and buccal surfaces.

Intertriginous regions (such as the anogenital region) offer an ideal place for yeasts to proliferate. The warm and moist skin folds, often with maceration or erosions, are main predisposing factors in the normal patients. Lesions are usually appearing as moist erythematous rash with characteristic satellite lesions that can be observed on the health surrounding skin.

Paronychia represents an inflammation of the tissue folds around the nail of a finger or toe that can be caused by Candida species. In acute cases (caused by trauma to the nail fold or cuticle) usually a painful and erythematous swelling around the affected nail is observed. In chronic paronychia separation of the cuticle from the nail plate is common.

Congenital cutaneous candidiasis represents an extremely rare disorder which presents within 72 hours of life of an infant (most often in premature babies). Diffuse and generalized skin eruption of maculopapular (and sometimes papulovesicular) rash is observed without any systemic symptoms such as hepatosplenomegaly, respiratory distress or sepsis.

Pityriasis versicolor and seborrheic dermatitis

Lipophilic yeasts of the genus Malassezia are constituents of the normal flora of human skin, typically recovered from up to 98% of healthy individuals. Still, they can be also associated with various diseases such as pityriasis versicolor and seborrheic dermatitis.

Under the influence of certain predisposing factors (such as high humidity and high temperature), Malassezia can change from the blastospore form to the mycelial form and cause pityriasis versicolor – a superficial infection of the stratum corneum usually located on the neck, upper arms and upper trunk.

On the other hand, seborrheic dermatitis represents a relapsing, chronic erythematous scaly cutaneous disease with the prevalence of 1 to 3% in the general population. In this case Malassezia can lead to a non-immunogenic irritation in susceptible individuals by producing unsaturated fatty acids and depositing them on the skin surface.

That in turn results in the development of red scaly lesions predominately found in the areas where sebum production is high (such as the face, the scalp, external ear with retroauricular region, eyelids and upper trunk). Patients with AIDS and those with neurological diseases (such as Parkinson’s disease) are commonly affected.

Dermatophytoses

Dermatophytoses are a group of fungal infection of the skin, hair or nails caused by dermatophyte fungi which necessitate keratin for growth. Most commonly involved is Trichophyton genus, whereas Microsporum or Epidermophyton genera are observed less commonly.

The most prevalent dermatophytosis in children is tinea capitis, which represents an infection of the scalp. The condition is characterized by scaling and well-demarcated alopecia, and is generally diagnosed by observing spores and branching hyphae on microscopy.

Tinea pedis – more commonly known as the athlete’s foot – is a dermatophytic infection of the plantar skin or interdigital areas of the foot. When nails are also affected, then the condition is known as tinea unguium (which is a subset of a broader condition known as onychomicosis).