Medical Today

Definition

Fungi are types of parasitic plants that include molds, mildew, and yeast. A fungal infection is an inflammatory condition in which fungi multiply and invade the skin, the digestive tract, the genitals, and other body tissues, particularly, the lungs and liver. Fungal infections of the skin are often called ringworm or tinea.

Description

Microscopic fungi, which are called dermatophytes, often live exclusively on such dead body tissues as hair, the outer layer of the skin, and the nails. The fungus grows best in moist, damp, dark places with poor ventilation and on skin that is irritated, weakened, or continuously moist. Superficial fungal infections include tinea capitis, an infection of the neck and scalp; tinea barbae, also called barber’s itch, along the beard area in adult males; tinea corporis on parts of the body, such as the arms, shoulders, or face; tinea cruris, or jock itch, involving the groin; tinea pedis, or athlete’s foot; tinea versicolor; and tinea unguium, or infection of the nails. The term tinea gladiatorum is sometimes used to describe ringworm infections in atheletes. Tinea gladiatorum is most common in swimmers, wrestlers, and athletes involved in other contact sports.

Fungal infections of the skin and nails are very common in children, but they can affect all age groups. Systemic fungal infections occur when spores are touched or inhaled, or there is an overgrowth of fungi in or on the body. Such infections are most often a serious problem in those with suppressed immune systems. Candidiasis is a rather common fungal infection. When it occurs in the mouth, it is called thrush. Less often, it occurs in the mucous membranes of other parts of the digestive system, or in the vagina, heart valves, urinary tract, eyes, or blood. Other systemic fungal infections include aspergillosis, which mostly affects the lungs and may also spread to the brain and kidneys; blastomycosis, a lung infection that may spread through the bloodstream; coccidioidomycosis, also known as San Joaquin or valley fever; mucormycosis, which can develop into a very serious, life-threatening infection; and histoplasmosis.

Causes & symptoms

Fungi are widespread in the environment, so it is not unusual that a certain amount of fungi and their spores end up being inhaled into the lungs or landing on the skin. Under conditions of moisture, warmth, irritation, or injury, these fungi grow rapidly and may cause illness. Superficial fungal infections may be due to an overgrowth of fungi already present, or the infection may be the result of contact with an infected person or with contaminated surfaces, bed sheets, towels, or clothing. Fungal infections can be spread from one part of the body to another by scratching or touching. Additionally, tinea unguium infections have been linked to the use of methyl methacrylate, a glue used for attaching acrylic fingernails.

Fungal spores are often present in soil and are likely to be inhaled when the soil is dug up or otherwise disturbed. Systemic fungal infections are commonly contracted in this way. In addition, fungi that normally inhabit the intestines, such as Candida albicans, may multiply, causing an infection due to an overgrowth of the fungi.

Tinea infections usually cause itchy, red, scaly, ring-shaped patches on the skin that spread easily. Hairs in the area of infection often fall out or break off, and the skin may crack. The skin may also develop a secondary bacterial infection. In tinea unguium, the nails discolor, crack, and thicken. Tinea versicolor may cause pigment changes in the skin that persist for up to a year.

Systemic fungal infections develop slowly. Symptoms often may be nonexistent, or there may be only the feeling of having a cold or the flu. Coughing, a fever, chest pain, chills, weight loss, and difficulty with breathing may become evident. Additional symptoms depend on the type and site of the infection. Fungal infections are more common and more severe in people taking antibiotics, corticosteroids, immunosuppressant drugs, and contraceptives. This is also the case in people with endocrine disorders, immune diseases, and other conditions such as obesity, AIDS, tuberculosis, major burns, leukemia, and diabetes mellitus.

Fungal infections often occur due to the use of antibiotic drugs for other conditions, because antibiotics kill off the bacteria that normally keep fungi at bay.

Diagnosis

Fungal infections of the skin, hair, and nails often can be diagnosed based on the characteristic appearance of affected areas. A KOH (potassium hydroxide) prep is a simple laboratory test to confirm the diagnosis. The test uses tissue samples treated with a 20% potassium hydroxide solution to detect fungi. Examining the skin with a Wood’s ultraviolet lamp is another easy and convenient method to determine the presence of a fungus.

Culture and sensitivity testing can be used if a more definitive diagnosis is required. Systemic fungal infections may be initially diagnosed from blood tests. Confirmation is determined by cultures made from sputum, blood, urine, bone marrow, or infected tissue samples.

Treatment

Superficial fungal infections are usually treated with such antifungal creams or sprays as tolnaftate (Aftate or Tinactin), clotrimazole, miconazole nitrate (Micatin products), econazole, ketoconazole, ciclopirox, naftifine, itraconazole, terbinafine, fluconazole, or Whitfield’s tincture made of salicylic acid and benzoic acid. If the infection is resistant, a doctor may prescribe an oral antifungal drug such as ketoconazole or griseofulvin. Drugs used for systemic infections include amphotericin B, which is highly toxic and is used for severe or life-threatening infections; the azoles, particularly fluconazole and itraconazole, which have been found to be the least toxic of these medications; and flucytosine alone or in combination with other antifungal medications. Fungal infections that become inflamed may be treated with a combination antifungal/steroid medication. Certain infections may require surgery.

Expected results

Infections usually respond to treatment within several weeks. However, many fungal infections are resistant to treatment, and it may take an extended time and repeated treatments to effect a cure. Infections may spread, and secondary bacterial infections may develop. Medications for fungal infections are often strong, and their use may cause such undesirable side effects as headache, dizziness, nausea, vomiting, or abdominal pain. Fungal infections are usually not serious in otherwise healthy individuals. However, a systemic fungal infection may be severe and life-threatening for those with compromised immune systems.

Prevention

Good personal hygiene should be maintained. In the case of superficial infections, the skin should be kept clean and dry, and care should be taken to avoid contact with other parts of the body. If someone in the household has a superficial fungal infection, bed sheets, towels, floors, shower stalls, and other contact surfaces should be washed with hot water and disinfected after use.