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Superficial Fungal Infections

»	What is a dermatophyte?
»	How are superficial fungal infections diagnosed?
»	On a KOH examination, hyphal-like structures arranged in a mosaic pattern are noted. Does this indicate the presence of a dermatophyte?
»	What are the three most commonly used culture media for the growth of dermatophytes?
»	Describe some of the presentations of superficial fungal infections caused by dermatophytes.
»	Which dermatophyte causes the most fungal infections of skin?
»	What is the most common cause of tinea capitis in the United States?
»	Name the four clinical patterns of tinea capitis.
»	What are the types of hair invasion in tinea capitis? What dermatophytes are associated with each type?
»	What is a Wood’s light? What organisms are detected by this exam?
»	How is tinea capitis treated?
»	What is meant by a carrier state in tinea capitis?
»	Name the three types of tinea pedis. Which dermatophyte is most commonly associated with each?
»	What nondermatophyte mold can cause mycotic infections that mimic moccasin-type tinea pedis?
»	What is a dermatophytid reaction?
»	Name and describe the four clinical presentations of onychomycosis.
»	Can other diseases mimic onychomycosis?
»	What is tinea versicolor?
»	How does Malassezia induce both hyperpigmentation and hypopigmentation in the skin?
»	How is tinea versicolor diagnosed? Why is it difficult to culture this organism?
»	Does Malassezia cause any other skin disease?
»	What is tinea nigra?
»	What is a Majocchi’s granuloma?
»	What is piedra?
»	Name the organism most commonly isolated from cutaneous candidiasis.
»	How do candidal infections present clinically?
»	What factors predispose to candidiasis?
»	Which diseases are associated with adult-onset chronic mucocutaneous candidiasis?
»	Name the different classes of oral antifungal agents and their mechanisms of action.
»	Which hepatic cytochrome is affected by itraconazole, ketoconazole, and fluconazole?
»	Which drugs should be used with caution when using ketoconazole, itraconazole, or fluconazole? Why?
»	Which drugs are contraindicated when using azole antifungal agents and why?
»	Which oral antifungal agents can lower cyclosporine levels?
»	Which drugs can affect antifungal drug levels?
»	Which antifungal drugs have a limited spectrum of activity in the treatment of superficial fungal infections?

What are the types of hair invasion in tinea capitis? What dermatophytes are associated with each type?

Fig. 31.3 Endothrix. Cross section of a hair shaft filled with hyphae and arthrospores (hematoxylin and eosin, [H&E]).

Dermatophytes can cause three types of hair invasion:

Endothrix infections are produced by fungi that invade the inside of the hair shaft and are composed of fungal arthroconidia and hyphae (Fig. 31-3). A helpful mnemonic to remember the organisms that cause endothrix invasion is: “TVs are in houses.”—T is Trichophyton tonsurans, V is violaceum, and S is soudanense.
Ectothrix infections are produced by fungi that primarily invade the outside of the hair shaft. Some agents of small-spore ectothrix cause a fluorescent tinea capitis.
Favus infections are characterized by invasion of hair by hyphae that do not produce conidia and by the presence of linear air spaces. T. schoenleinii is associated with this type of invasion.