Fungi are living organisms made up of chains of cells, called hyphae, which grow and become intertwined and matted, forming mycelia and spores. In everyday life they can be seen as the mould on old fruit or cheese. There are between 50 000 and 100000 known species throughout the plant and animal kingdom, and they are all parasites. Some are useful and productive, such as those which are used to produce Penicillin and the antifungal antibiotic, Griseofulvin. Relatively few cause problems in man. Those that do. however, affect many millions of people. It is estimated that 15 million individuals throughout the world have ringworm of the scalp!
The fungi which cause tinea are called dermatophytes. There are three species of dermatophytes: Microsporum, which rarely affects the nails; Epidermophyton, which rarely affects hair, and Trichophyton. All of them affect the epidermis of the skin. Some species are almost solely confined to humans, and these cause milder but more persistent infections than do some other species. Those species which normally infect animals, cause a more severe but less prolonged infection when contracted by man. Some species normally found in the soil may cause tinea in animals or man.
Tinea Cnpitits (’Scalp Ringworm’). This is almost entirely a disease of children, and is mainly transmitted from cats and dogs or from other children. With this disease the appearance of the scalp is one of well-defined areas of Inflammation and hair loss. The condition is most easily diagnosed by a fluorescence of the infected hair shaft when it is placed under an ultra-violet Woods lamp.
Tinea Corporis (’Body Ringworm’). This occurs at all ages and in all races, being more common in warm, humid climates. It may be acquired from infected animals and humans, or from infection of the patient’s own nails and feet. The classical ‘ringworm’ begins as a red pimple which enlarges peripherally, with relative clearing centrally. The border is raised, red and well defined. Frequently, it may be confused with discoid eczema. Unfortunately the appearances are not always classical and tinea may occur with many bizarre features.
The diagnosis is either made on direct examination of affected skin under the microscope or on cultures of the scrapings.
Infected skin does not, unfortunately, fluoresce under the Wood’s lamp.
Tinea Cruris (’Bobbie itch’). Fungal infections of the groin are commoner in men than in women. Tinea cruris is predominantly a summer disease, and its appearance is made more likely by the wearing of tight occlusive clothing, particularly nylon. Transmission by towels and other objects may occur, particularly in saunas and communal showers. Cross-infection from the feet is also common. The infection usually begins on the upper inner thigh, with a well-defined border which gradually extends. It is commonly itchy, but never involves the scrotum.
Tinea Pedis (’Athletes foot’). This is a common problem, but the mechanism of transmission is ill understood. Although this disease is more common in hot, humid climates, it virtually only affects people who wear shoes-it is rare, for example, amongst barefooted natives. The fungus is thought to be acquired by walking barefoot on fragments of infected skin or nail, particularly around swimming pools or in communal showers. It is uncommon in women, and very rare in children. Children with eczema of the toes are frequently thought, incorrectly, to suffer from tinea because the appearance of the two conditions is similar.
The infection may have symptoms of softening and cracking of the skin between the toes, ft may also appear as blisters or a diffuse scaling on the soles of the feet. It is very rare on top of the foot.
Tinea of the nails. This infection is almost always confined to adults, and is usually caused by the same fungus which affects the skin. The earliest change is usually a small area of white, yellow, or brown discolouration on one side of the nail, close to the cuticle. This discolouration spreads, and may involve the whole nail. Keratin tissue may build up under the nail and lift it from its bed. The nail may also crumble away, or become thick and distorted. These changes may be easily confused with either paronychia, which is a yeast and bacterial infection of the nailfold, or psoriasis, which has similar features but is not an infection.
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