• Secondary to transformation of Malassezia spp., especially M. furfur, from the yeast form to the hyphal form (see Fig. 2.1A).

• Malassezia spp. are part of the normal flora.

• Multiple, brown (hyperpigmented), tan (hypopigmented), or pink, oval to round macules, patches, or thin plaques; there is often coalescence of lesions centrally with scattered lesions at the periphery.

• Associated scale may be subtle but becomes more obvious with gentle scratching or stretching of the skin.

• Most commonly develops on the upper trunk and shoulders, but can also involve flexural sites such as the antecubital fossae, submammary folds, and groin (Fig. 64.1); in children more frequently than adults, there can also be facial involvement.

• Often first noticed in the summer, and a suntan accentuates the hypopigmented variant.

• DDx: postinflammatory hypopigmentation and idiopathic macular hypomelanosis (if hypopigmented); confluent and reticulated papillomatosis of Gougerot and Carteaud (if hyperpigmented; see Chapter 89).

• Rx: outlined in Table 64.1.

• Following appropriate Rx, the associated hypopigmentation may persist for months until there is repigmentation or fading of the suntan.

• Typically seen in tropical areas.

• Tinea nigra.

– Most commonly due to infection with Hortaea werneckii, a pigmented fungus found in soil.

– Brown, sharply marginated macule or patch; most commonly on the palms (Fig. 64.2).

– Rx: keratolytic agents (e.g. salicylic acid 6% cream) and topical antifungals (e.g. terbinafine 1% cream).

• Black piedra and white piedra are characterized by the formation of nodules on hair shafts (Table 64.2; Fig. 64.3).

• The names of dermatophyte infections consist of the word ‘tinea’ followed by the Latin name for the involved body site; examples are tinea pedis (foot) and tinea cruris (groin) (Fig. 64.4).

• Due to fungi of three genera – Trichophyton, Microsporum, and Epidermophyton – that invade only keratinized tissue (stratum corneum, hair, and nails).

– With the exception of tinea capitis, Trichophyton rubrum and T. mentagrophytes are the most common pathogens.

– Trichophyton mentagrophytes has two major variants that infect the skin, which can lead to confusion; T. mentagrophytes var. interdigitale is spread human-to-human, whereas T. mentagrophytes var. mentagrophytes is acquired from animals; these variants are also known as T. interdigitale [anthropophilic] and [zoophilic], respectively.

• Transmission occurs via close contact with infected humans or domestic animals, occupational or recreational exposure (e.g. locker rooms), and contact with contaminated clothing, furniture, or brushes; the latter inanimate objects serve as fomites.

• More commonly seen in adults, with the exception of tinea capitis, which occurs more often in children.

• The classic presentation is an erythematous, annular lesion with an active, scaly border; superficial pustules may also be present (Fig. 64.5).

• Occasionally, vesicles may develop, especially in tinea pedis or manuum due to T. mentagrophytes.

• Dx: KOH ± fungal culture of skin scrapings (see Fig. 2.1) as well as hairs and nails, in the case of tinea capitis and tinea unguium, respectively.

• Important variants:

– Tinea incognito refers to atypical clinical presentations, often due to inappropriate treatment with potent topical CS or combination topical therapies that contain CS; lesions may lack scale or be minimally inflamed (Fig. 64.6; see Fig. 64.5E).

– Majocchi’s granuloma is characterized by erythematous papules or pustules within an area of tinea corporis; the papules represent sites of hair shaft invasion, usually due to T. rubrum; often seen in women with tinea pedis who shave their legs or in immunosuppressed patients (see Fig. 31.4A; Fig. 64.7).

• Tinea pedis (Fig. 64.8).

– Most commonly due to T. rubrum or T. mentagrophytes var. interdigitale > Epidermophyton floccosum.

– Three major types: (1) interdigital – erythema, scaling, and maceration in the web spaces, especially the two lateral web spaces, which have the most occlusion; can be accompanied by fissures as well as superimposed bacterial infection; (2) moccasin – diffuse scaling and erythema that extends onto the lateral aspect of the feet; and (3) inflammatory (vesicular) – vesicles and bullae, especially on the medial aspect of the plantar surface.

– Occasionally, especially in immunocompromised and diabetic patients, a more severe ulcerative toe-web infection can occur where there is both a dermatophyte and a bacterial (e.g. pseudomonal) infection; see discussion of gram-negative toe-web infection in Chapter 61.

– Consider use of oral antifungal medications if the tinea pedis fails to respond to topical agents or is severe (Table 64.3).