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INTRODUCTION

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The least invasive of the pathogenic fungi are the dermatophytes and other superficial fungi that are adapted to the keratinized outer layers of the skin. The subcutaneous fungi go a step farther by extending infection to the tissue beneath the skin but rarely invading deeper structures (Table 45–1).

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TABLE 45–1abcdefAgents of Superficial and Subcutaneous Mycoses
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SUPERFICIAL FUNGI

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Overview

Dermatophytoses are slowly progressive eruptions of the skin and its appendages. Although often unsightly, they are not typically painful or life-threatening. The manifestations vary depending on the site of infection and vigor of the host response, but they often involve erythema, induration, itching, and scaling. The most familiar name is “ringworm,” describing the annular shape of the advancing edge of this cutaneous infection.

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Dermatophytes

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Dermatophytoses are superficial infections of the skin and its appendages. Common names for these infections include ringworm (Figure 45–1), athlete’s foot, and jock itch. They are caused by species of three genera collectively known as dermatophytes. These fungi are highly adapted to the nonliving, keratinized tissues of nails, hair, and the stratum corneum of the skin. The source of infection may be humans, animals, or the soil.

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FIGURE 45–1.

Ringworm. The ring-like lesions on this forearm are due to advancing growth of Trichophyton mentagrophytes. (Reproduced with permission from Willey JM: Prescott, Harley, & Klein’s Microbiology, 7th edition. McGraw-Hill, 2008.)

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