Diseases of the skin that are caused by fungus and that can range from a mild to a fatal condition. Fungi are a phylum of plants including yeasts, rusts, slime molds, smuts, and mushrooms that are characterized by the absence of chlorophyll and the presence of a rigid cell wall.
A fungus is actually a primitive vegetable that can be found in air, in soil, on plants, and in water. There are more than 100,000 different species of fungi around the world, most of which are harmless or beneficial to human health (such as molds used to produce antibiotics, yeasts used in baking and brewing, edible mushrooms and truffles, and so on).
However, some fungi can invade and form colonies in the skin or underneath the skin, leading to disorders ranging from a mild skin irritation and inflammation to severe or fatal systemic infections. Only about half of all types of fungi cause disease in humans; those conditions are called mycoses. Mycoses can affect the skin, nails, body hair, internal organs (such as the lungs), or body systems such as the nervous system.
Fungi reproduce by sending out spores (cells that resemble plant seeds). When a spore lands in a moist place, it sends out small threads from which the fungus feeds. These moist places that support fungi include dead plant and animal matter and bacteria.
The superficial fungal infections include THRUSH (candidiasis) and TINEA (including ringworm and athlete’s foot). Subcutaneous infections are rare; the most common is sporotrichosis, occurring after a scratch becomes contaminated; most examples of this type of condition occur in tropical climates.
Harmless fungi are present all the time on the skin, but they do not multiply there because of bacterial competition or because the body’s immune system fights them off. Fungal infections of the skin are most common in those taking long-term antibiotics or those taking corticosteroid or immunosuppressant drugs, or in patients with an immune system disorder such as AIDS.
Physicians use three classes of drugs to fight fungal disease, but in the past five years disease-causing fungi have begun to grow resistant to common drugs, just like some types of bacteria. Strains of fungi resistant to each of the three types of drugs are now common in hospitals that care for the sickest patient —especially patients with cancer and AIDS. This growing resistance appears to have developed for the same reasons that bacteria have grown impervious: the overuse of drugs to combat fungal infections.
High use of antifungal medications occurred because of the large number of people with impaired immune systems due to AIDS and chemotherapy. Between five and 10 percent of AIDS patients now have resistant fungi that cause oral CANDIDIASIS, a common mouth infection.