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Fungal Overview

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Patient Story
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An otherwise healthy 7-year-old boy is seen in a homeless shelter with a 2-month history of patchy hair loss (Figure 120-1). Various anti-dandruff shampoos had not helped. On physical exam, there are moderate areas of patchy alopecia with significant scaling of the scalp. Posterior cervical adenopathy could be seen and palpated on the left side. There was no fluorescence with a Wood’s lamp indicating that this fungal infection was most likely Trichophyton tonsurans. The pediatrician easily identified this as tinea capitis but decided to confirm the diagnosis with a KOH preparation. Some of the scale was scraped from the scalp using two microscope slides (one to scrape and another to catch the scale). KOH was added and a coverslip placed. Branching hyphae were seen under the microscope. The child was treated with oral griseofulvin at 20 mg per kilogram per day. At the 4-week follow-up there was significant improvement, no reported side effects of the griseofulvin, and the treatment was continued for an additional 4 weeks.

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FIGURE 120-1

Tinea capitis in a young African American boy showing patchy alopecia and posterior cervical adenopathy. (Used with permission from Richard P. Usatine, MD.)

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Introduction
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Fungal infections of the skin and mucous membranes are ubiquitous and common. There are many types of fungus that grow on humans but they all share a predilection for warm and moist areas. Consequently, hot and humid climates promote fungal infections, but many areas of the skin can get warm and sweaty even in cold climates, such as the feet and groin.

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Synonyms
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Pityriasis versicolor equals tinea versicolor.

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Pathophysiology
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Mucocutaneous fungal infections are caused by:

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  • Dermatophytes in three genera: Microsporum, Epidermophyton, and Trichophyton. There are approximately 40 species in the three genera and these fungi cause tinea pedis and manus, tinea capitis, tinea corporis, tinea cruris, tinea faciei, and onychomycosis (Figures 120-1 to 120-6).

  • Yeasts in the genera of Candida and Pityrosporum (Malassezia)—There are also multiple types of species and the Pityrosporum that cause seborrhea and tinea versicolor (Figures 120-7 and 120-8). Although tinea versicolor has the name tinea in it, it is not a true dermatophyte and may be best called pityriasis versicolor.

  • There are a number of deep fungal skin infections that can occur in humans. They are all rare and will not be covered in this chapter which focuses on dermatophyte and yeast organisms. One deep fungal infection that is less rare is Sporotrichosis and can occur from minor trauma with a rosebush thorn (Figure 120-9).

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FIGURE 120-2

Annular pruritic lesion with concentric rings in the axilla of a young woman caused by ...

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