Chapter 135. Fungal Overview

A 55-year-old woman presents with a red pruritic area on her face for 3 months (Figure 135-1). The annular distribution immediately is suspicious for a dermatophyte infection. Further investigation demonstrates that the patient has severe tinea pedis in a moccasin distribution. The patient is treated with an oral antifungal agent and her fungal infection clears over the coming month.

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.

Pityriasis versicolor equals tinea versicolor.

Mucocutaneous fungal infections are caused by:

• 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 135-1 to 135-6).
• 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 135-7 and 135-8). Although tinea versicolor has the name tinea in it, it is not a true dermatophyte and may be best called pityriasis versicolor.

Clinical Features of Tinea Infections

Scaling, erythema, pruritus, central clearing, concentric rings, and maceration (Table 135-1). Changes in pigmentation are not uncommon in various types of tinea especially tinea versicolor.

• Figure 135-1 shows tinea faciei on the face with typical scaling and ring-like pattern, hence, the name ringworm. There is also erythema and central clearing. The patient was experiencing pruritus.
• Figure 135-2 shows annular pruritic lesion with concentric rings in the axilla of a young woman caused by tinea corporis. The concentric rings have a high specificity (80%) for tinea infections.
• Note that tinea infections will not show central clearing in 58% of cases, as in Figure 135-3 in which tinea cruris has no central clearing.
• Post-inflammatory hyperpigmentation is common in skin of color, as seen in Figure 135-4. Note the hyperpigmentation is seen within the area affected by the tinea corporis.
• Hypopigmentation is frequently seen in tinea versicolor (Figure 135-8).

Typical Distribution

Literally found from head to toes:

• Figure 135-5 shows tinea capitis in a 5-year-old black girl with hair loss and an inflammatory response. Her kerion is healing after initiating oral griseofulvin.
• The two-foot, one-hand syndrome is a curious phenomenon with tinea manus of one hand and tinea pedis of both feet (Figure 135-6). It is not clear why only one hand is involved in these cases. In this case, it was the nondominant hand.

Laboratory Studies

Creating a KOH Prep:

• Scrape the leading edge of the lesion on to a slide using the side of a #15 scalpel or another microscope slide (Figure 135-9).
• Use your coverslip to push the scale into the center of the slide.
• Add two drops of KOH (or fungal stain) to the slide and place coverslip on top.
• Gently heat with flame from an alcohol lamp or lighter if you are using plain KOH without dimethyl sulfoxide (DMSO). Avoid boiling.
• DMSO acts as a surfactant that helps to break up the cell membranes of the epithelial cells without heating. Fungal stains that come with KOH and a surfactant in the solution are very simple to use. These inexpensive stains come conveniently in small plastic squeeze bottles that have a shelf life of 1 to 3 years. Two useful stains that can that make it easier to identify fungus are chlorazol and Swartz-Lamkins stains. Swartz-Lamkins stain has a longer shelf life and is my preferred stain.
• Examine with microscope starting with 10 power to look for the cells and hyphae and then switch to 40 power to confirm your findings (Figures 135-10, 135-11, 135-12, and 135-13). The fungal stain helps the hyphae to stand out among the epithelial cells.
• It helps to start with 10 power to find the clumps of cells and look for groups of cells that appear to have fungal elements within them (Figure 135-10).
• Do not be fooled by cell borders that look linear and branching. True fungal morphology at 40 power should confirm that you are looking at real fungus and not artifact. The fungal stains bring out these characteristics including cell walls, nuclei, and Arthroconidia (Figures 135-11, 135-12, and 135-13).
• KOH test characteristics1 (without fungal stains)—Sensitivity 77% to 88%, specificity 62% to 95% (Table 135-2). The sensitivity and specificity should be higher with fungal stains and the experience of the person performing the test.

Other Laboratory Studies

• Fungal culture—Send skin scrapings, hair, or nail clippings to the laboratory in a sterile container such as a urine cup. These will be plated out on fungal agar and the laboratory can report the species if positive.
• Biopsy specimens can be sent in formalin for periodic acid-Schiff (PAS) staining when KOH and fungal cultures seem to be falsely negative.
• UV light (Woods lamp), looking for fluorescence. The Microsporum species are most likely to fluoresce. However, the majority of tinea infections are caused by Trichophyton species that do not fluoresce.

There is a wide variety of topical antifungal medications (Table 135-3). A Cochrane systematic review of 70 trials of topical antifungals for tinea pedis showed good evidence for efficacy compared to placebo2 for:

• Allylamines (naftifine, terbinafine, butenafine).
• Azoles (clotrimazole, miconazole, econazole).
• Allylamines cure slightly more infections than azoles but are more expensive.2
• No differences in efficacy found between individual topical allylamines or individual azoles.2 SOR A

Evidence for the management onychomycosis by topical treatments is sparse. There is some evidence that ciclopiroxolamine and butenafine are both effective, but they both need to be applied daily for at least 1 year.3

Oral antifungals are needed for all tinea capitis infections and for more severe infections of the rest of the body.4 True dermatophyte infections that do not respond to topical antifungals may need an oral agent.

• A Cochrane systematic review of 12 trials of oral antifungals for tinea pedis showed oral terbinafine for 2 weeks cures 52% more patients than oral griseofulvin.5 SOR A
• Terbinafine is equal to itraconazole in patient outcomes.5
• No significant differences in comparisons between a number of other oral agents.5

Oral antifungals used for fungal infections of the skin, nails, or mucous membranes:

• Itraconazole (Sporanox).
• Fluconazole (Diflucan).
• Griseofulvin.
• Ketoconazole (Nizoral).
• Terbinafine (Lamisil).

One metaanalysis suggests that terbinafine is more efficacious than griseofulvin in treating tinea capitis caused by Trichophyton species, whereas griseofulvin is more efficacious than terbinafine in treating tinea capitis caused by Microsporum species.6 SOR A

Details of treatments for multiple types of fungal skin infections are supplied in the following chapters.

Patient Resources

• Doctor fungus—http://www.doctorfungus.org/.

Provider Resources

• Fungal skin from New Zealand—http://www.dermnetnz.org/fungal/.
• Doctor fungus from the United States—http://www.doctorfungus.org/.
• World of dermatophytes from Canada—http://www.provlab.ab.ca/mycol/tutorials/derm/dermhome.htm.
• Swartz Lamkins fungal stain can be easily purchased online at—http://www.delasco.com/pcat/1/Chemicals/Swartz_Lamkins/dlmis023/.