Fungal infections are common but tend to resolve completely with treatment.
Fungi are ubiquitous and present in all environmental niches (eg, soil, plants, trees, indoor surfaces, human skin). There are roughly 1.5 million different species of fungi, a handful of which are responsible for the majority of unsightly, often embarrassing skin infections. The health care community began to shine the spotlight on fungal infections in the late 20th century: at that time, the spread of HIV created large populations of immunologically impaired people with heightened susceptibility to raging, potentially lifethreatening fungal infections.1,2

The Fungi Story
Fungi were originally classified as plants—think, grocery-store mushrooms— and many people are unaware that these chlorophyll- and cell wall–deficient organisms are not plant species. Most fungi thrive at temperatures between 53.6°F and 86°F (12°C-30°C). Mammals’ high body temperatures compared with ambient temperatures endow them with protective endothermy (inhospitable temperature for fungal growth) against fungi that enter the body.2

The approximately 300 fungi that cause disease in humans are primarily dermatophytes—they infect our outer skin—and they are classified by the area they infect. Fungi need warmth and moisture, making sweaty feet, skin folds, and mucous membranes attractive. Some fungi are yeast-like, causing infections such as candidiasis, while others are mold-like, causing tinea infections. This article examines the most common fungal skin infections3 (Online Table4-6).

Candidiasis
Candida yeasts grow on the skin’s surface. Antibiotic use or immune system dysfunction creates opportunities for oral, digestive, or vaginal overgrowth. Candida fungi prefer moist areas, making Candida a common cause of diaper rash, rash in obese patients’ skin folds, and vaginal infections. Candida infection often responds to nystatin.5,6

Athlete’s Foot, Jock Itch, and Ringworm
Three types of fungal infection are closely related:
  • Tinea pedis (athlete’s foot): on any given day, 20% of Americans are infected (most of them are men). Risk factors include wearing athletic shoes that retain warmth and perspiration and using public athletic facilities. Most patients can treat athlete’s foot successfully with an OTC topical antifungal, although severe cases require a prescription product. Recurrence is common, even after prolonged treatment.6,7
  • Tinea cruris (jock itch): this infection frequently follows athlete’s foot and is characterized by burning, scaly, and itchy skin. It typically affects young males, although women can contract it, as well. Some clinicians counsel patients infected with athlete’s foot to put socks on before underwear to prevent the infection’s spread.6,7
  • Tinea corporis (ringworm—a misnomer, it’s not a worm): highly contagious, ringworm forms on the trunk or extremities, and affects more women than men. Ringworm’s vectors are shared clothing and towels, direct contact with others who are infected, and companion animals.6,7 These 3 infections usually respond to topical treatment with terbinafine, butenafine, or luliconazole. Extensive or severe infection, however, may require oral antifungals.6-8

Tinea Capitis
Tinea capitis (scalp infection) attacks scalp, eyebrow, and eyelash hair follicles and is typically diagnosed in African American children aged 3 to 9 years. Topical agents cannot penetrate the hair shaft, necessitating oral treatment. Terbinafine and fluconazole have largely displaced griseofulvin, the older drug of choice, because they are safe and effective and produce results faster. Patients who use selenium or ketoconazole shampoo for the first 2 weeks are less likely to spread the infection to others.9-11

Pityriasis Versicolor
Pityriasis versicolor (skin infection [formerly tinea versicolor]) usually thrives in warm and humid environments. People who have seborrheic dermatitis, dandruff, and hyperhidrosis seem to acquire the infection more than others, yet the factors promoting its growth are poorly understood. Patients often complain of itching or flaking. Treatments include topical selenium sulfate, ketoconazole, terbinafine, or ciclopirox.5,12 Oral antifungals can also be used. Although longer therapy treatments are more effective, some clinicians prescribe a single dose and then direct the patient to exercise heavily 1 to 2 hours later to induce sweating. Patients then allow the sweat to evaporate, and delay showering for a day, which leaves a film of the medication on the skin.13

Onychomycosis
Onychomycosis (nail infection) can be painful, disfiguring, and psychologically disconcerting as the fungus invades the nail bed and inflammation occurs. Onychomycosis is usually treated with 3 to 6 months of oral therapy. Prescribers often choose oral terbinafine because of its superior effectiveness, tolerability, and low cost, but oral fluconazole is also effective.4,14 Medication frequently fails, however. The FDA recently approved efinaconazole, a topical product that is used once daily for 48 weeks.15 Patients need to be reminded that it takes 9 to 12 months for the disfigured nail to grow out. Up to 50% of infections recur.4,14 Laser treatment can also cure onychomycosis.4,16

Endnote
Fungal infections are common. Once treated, however, they tend to resolve completely. The Sidebar lists points to remember regarding dermal fungi.


Ms. Wick is a visiting professor at the University of Connecticut School of Pharmacy.


Table: Common Fungal Skin Infections
Infection Usual Pathogen Signs and Symptoms
Candidiasis
 
Yeasts of the genus Candida ·         Cutaneous candidiasis is usually red, flaky, and itchy
·         Oral thrush is usually caused by Candida albicans, and ordinarily presents with white patches or plaques on the tongue and other oral mucous membranes; redness or soreness; dysphagia; and angular cheilitis (cracking at the corners of the mouth)
·         Uncommon among healthy adults
Pityriasis versicolor (formerly tinea versicolor) Yeasts of the genus Malassezia ·         Marked skin discoloration (lightening or darkening), usually on the oily skin of the chest and back, and occasionally the neck and upper arms
·         Lesions appear white, brown, tan, or pink
Tinea capitis Trichophyton tonsurans
Microsporum audouinii
Microsporum canis
·         Occurs on the scalp, and usually starts with itching and scaling
·         Often causes alopecia or dotted areas of inflammation
·         May progress to kerion (boggy
tender plaques and pustules)
Tinea corporis (ringworm) Trichophyton rubrum
M canis
T tonsurans
Trichophyton verrucosum
·         Red, itchy; 1- to 5-cm circular rash
·         Often mistaken for eczema; worsens after treatment with steroids
·         Initial red pustular lesions; patches spread quickly
·         Chronic infection is possible, and its milder rash spreads slowly
Tinea cruris (jock itch) T rubrum
Epidermophyton floccosum
·         Appears around the groin, anus, and inner thighs, usually sparing the penis and scrotum
·         The rash’s center can become reddish-brown, while the edges develop scale, bumps, or oozing blisters
Tinea pedis (athlete’s foot) T rubrum
Trichophyton mentagrophytes var interdigitale
E floccosum
·         Burning and itching are hallmark symptoms; some people develop blisters; skin lesions on the heels, soles, or along the sides of the feet; or fissures between toes
Tinea unguium (onychomycosis) T rubrum
Trichophyton mentagrophytes var mentagrophytes
·         Causes dystrophic, thick, brittle, discolored nails
A slide presentation with clear pictures is available at http://reference.medscape.com/features/slideshow/cfi.
Adapted from references 4-6.
 
Sidebar: Treating Tinea Infections: Points to Remember
·         Dermatophytes are resistant to nystatin, so it is an inappropriate treatment. Nystatin is often effective for treating cutaneous Candida infections.
·         Avoid oral ketoconazole because it can cause hepatic toxicity; other drugs are safer.
·         Terbinafine is usually a better option than griseofulvin for treating onychomycosis.
·         Avoid using combination products containing corticosteroids; they can aggravate fungal infections.
·         Topical butenafine and terbinafine are more effective than topical clotrimazole or miconazole.
·         For treating tinea capitis, an oral agent is needed and should be combined with a sporicidal shampoo (selenium sulfide or ketoconazole).
Adapted from references 4-6 and 17.

References
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  2. Hawksworth DL. The magnitude of fungal diversity: the 1.5 million species estimate revisited. Mycol Res. 2001;105(12):1422-1432.
  3. Segal E, Frenkel M. Dermatophyte infections in environmental contexts. Res Microbiol. 2015; S0923-2508(14)00256-3. doi: 10.1016/j.resmic.2014.12.007.
  4. de Berker D. Clinical practice. Fungal nail disease. N Engl J Med. 2009;360(20):2108-2116. doi: 10.1056/NEJMcp0804878.
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  10. Chen C, Koch LH, Dice JE, et al. A randomized, double-blind study comparing the efficacy of selenium sulfide shampoo 1% and ciclopirox shampoo 1% as adjunctive treatments for tinea capitis in children. Pediatr Dermatol. 2010;27(5):459-462. doi: 10.1111/j.1525-1470.2010.01093.x.
  11. Elewski BE, Cáceres HW, DeLeon L, et al. Terbinafine hydrochloride oral granules versus oral griseofulvin suspension in children with tinea capitis: results of two randomized, investigator-blinded, multicenter, international, controlled trials. J Am Acad Dermatol. 2008;59(1):41-54. doi: 10.1016/j.jaad.2008.02.019.
  12. Rad F, Nik-Khoo B, Yaghmaee R, Gharibi F. Terbinafin 1% cream and ketoconazole 2% kream in the treatment of pityriasis versicolor: a randomized comparative clinical trial. Pak J Med Sci. 2014;30(6):1273-1276. doi: 10.12669/pjms.306.5509.
  13. Rivard SC. Pityriasis versicolor: avoiding pitfalls in disease diagnosis and therapy. Mil Med. 2013;178(8):904-906. doi: 10.7205/MILMED-D-13-00057.
  14. Gupta AK, Ryder JE, Johnson AM. Cumulative meta-analysis of systemic antifungal agents for the treatment of onychomycosis. Br J Dermatol. 2004;150(3):537-544.
  15. Rich P. Efinaconazole topical solution, 10%: the benefits of treating onychomycosis early. J Drugs Dermatol. 2015;14(1):58-62.
  16. Li Y, Yu S, Xu J, Zhang R, Zhao J. Comparison of the efficacy of long-pulsed Nd:YAG laser intervention for treatment of onychomycosis of toenails or fingernails. J Drugs Dermatol. 2014;13(10):1258-1263.
  17. Five things physicians and patients should question. Choosing Wisely website. www.choosingwisely.org/doctor-patient-lists/american-academy-of-dermatology/. Published October 29, 2013. Accessed February 28, 2015.