Mycosis

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Synonyms and keywords: Fungus and fungal infections; mycete; mycoses; fungus infections

Overview

The Term mycosis (plural: mycoses) refers to conditions in which fungi pass the resistance barriers of the human or animal body and establish infections. Mycoses are common, and a variety of environmental and physiological conditions can contribute to the development of fungal diseases. Inhalation of fungal spores or localized colonization of the skin may initiate persistent infections; therefore, mycoses often start in the lungs or on the skin.

Causes

People are at risk of fungal infections when they are taking strong antibiotics for a long period of time because antibiotics kill not only damaging bacteria, but healthy bacteria as well. This alters the balance of microorganisms in the mouth, vagina, intestines and other places in the body, and results in an overgrowth of fungus.

Individuals with weakened immune systems are also at risk of developing fungal infections. This is the case of people with HIV/AIDS, people under steroid treatments, and people taking chemotherapy. People with diabetes also tend to develop fungal infections. Very young and very old people, also, are groups at risk.

Classification

Mycoses are classified according to the tissue levels initially colonized:

1. Superficial mycoses - limited to the outermost layers of the skin and hair.
2. Cutaneous mycoses - extend deeper into the epidermis, as well as invasive hair and nail diseases. These diseases are restricted to the keratinized layers of the skin, hair, and nails. Unlike the superficial mycoses, host immune responses may be evoked, resulting in pathologic changes expressed in the deeper layers of the skin. The organisms that cause these diseases are called dermatophytes. The resulting diseases are often called ringworm (even though there is no worm involved) or tinea. Cutaneous mycoses are caused by Microsporum, Trichophyton, and Epidermophyton fungi, which together comprise 41 species.
3. Subcutaneous mycoses - involve the dermis, subcutaneous tissues, muscle, and fascia. These infections are chronic and can be initiated by piercing trauma to the skin, which allows the fungi to enter. These infections are difficult to treat and may require surgical interventions such as debridement.
4. Systemic mycoses due to primary pathogens - originate primarily in the lungs and may spread to many organ systems. Organisms that cause systemic mycoses are inherently virulent. Generally, primary pathogens that cause systemic mycoses are dimorphic.
5. Systemic mycoses due to opportunistic pathogens - infections of patients with immune deficiencies who would otherwise not be infected. Examples of immunocompromised conditions include AIDS, alteration of normal flora by antibiotics, immunosuppressive therapy, and metastatic cancer. Examples of opportunistic mycoses include Candidiasis, Cryptococcosis and Aspergillosis.

Another example of a fungal infection is Tinea versicolor: Tinea versicolor is a fungus infection that commonly affects the skin of young people, especially the chest, back, and upper arms and legs. Tinea versicolor is caused by a fungus that lives in the skin of almost all adults. It doesn't usually affect the face. This fungus produces spots that are either lighter than the skin or a reddish-brown. There may be just a few spots or lots of spots. Tinea versicolor is caused by a fungus that lives in the skin of almost all adults. This fungus exists in two forms, one causes visible spots. Factors that can cause the fungus to become more visible include high humidity and immune or hormone abnormalities. But almost all people with this very common condition are healthy.

Treatment

Antifungal drugs are used to treat mycoses. Depending on the nature of the infection, a topical or systemic agent may be used. Photochemotherapy or photopheresis is a technique used at major medical centers for the treatment of mycosis fungoides.

An example of antifungal is fluconazole, or Diflucan, which is the basis of many over-the-counter antifungal treatments. Another example is amphotericin B (the A form being toxic) which is more potent. It is used in the treatment of the most severe fungal infections that show resistance to other forms of treatment and it is administered intravenously.

Drugs to treat skin infections are Tolnaftate (Tinactin), an over the counter topical; Ketoconazole, especially used to treat tinea versicolor and other dermatophytes; Itraconazole; Terbinafine (Lamisil); Echinocandins (caspofungin); Griseofulvin, commonly used for infections involving the scalp and nails.

Yeast infections in the vagina, caused by candida albicans, can be treated with medicated suppositories and pessaries whereas skin yeast infections are treated with medicated ointments.

Contraindicated Medications

• Dexamethasone
• Prednisolone
• Prednisone

Prevention

Keeping the skin clean and dry, as well as maintaining good hygiene, will help prevent topical mycoses. Because fungal infections are contagious, it is important to wash after touching other people or animals. Sports clothing should also be washed after use. Wearing flip-flops when using a community swimming pool or shower will also prevent topical infections.

Related Chapters

• Dermatophytosis
• Pathogenic fungi
• Black hairy tongue