Dermatophyte Infections

Tinea Pedis (“Athlete's foot”)

Basics

Tinea pedis is an extremely common problem seen mainly in young men. Ubiquitous media advertisements for athlete's foot sprays and creams are testimony to the commonplace occurrence of this annoying dermatosis.
Most cases are caused by T. rubrum, which evokes a minimal inflammatory response and less often by T. mentagrophytes, which may produce vesicles and bullae. Much less frequently, Epidermophyton floccosum may be the causative agent.
There are three distinguishable clinical forms: type 1: interdigital; type 2: chronic plantar; and type 3: acute vesicular.

Clinical Variants

Type 1: Interdigital Tinea Pedis

The most common type of tinea pedis is seen predominantly in men between the ages of 18 and 40 years and is unusual in children.
Often asymptomatic; however, may itch intensely.
Scale, maceration, and fissures are characteristic (Fig. 18.1).
Toe web involvement especially between the third and fourth and the fourth and fifth toes; however, any web space may be involved (Fig. 18.2).
Marked inflammation and fissures suggest secondary bacterial superinfection.

Type 2: Chronic Plantar Tinea Pedis

Chronic plantar tinea pedis is also called the “moccasin” type of tinea pedis.
Symptoms are absent or minimal (e.g., itching); however, painful fissures may occur.
Patients are often not aware of this, and if untreated it usually persists indefinitely.
Lesions consist of diffuse or focal, asymptomatic scaling of the soles that are often considered to be “dry skin” by patients.
Over time, the entire plantar surface of the foot becomes involved.
Borders are distinct along the sides of the feet (“moccasin” distribution) (Figs. 18.3 and 18.4).
There is often nail involvement.

“Two Feet, One Hand” (Palmar/Plantar) Tinea Pedis

Tinea can present on one or both palms (tinea manuum). Not infrequently, it appears in a “two feet, one hand” distribution. This is pathognomonic for tinea (Fig. 18.5). Nail dystrophy (onychomycosis) is also often present.
Management is similar to that for chronic tinea pedis.

Type 3: Acute Vesicular Tinea Pedis

This is the least common clinical variant of tinea pedis.
Tends to be quite pruritic.
Vesicles and bullae generally occur on the sole, great toe, and instep of the foot (Fig. 18.6).

Diagnosis

A positive KOH examination or fungal culture is diagnostic.
In acute vesicular tinea pedis, specimens taken for KOH or culture should be obtained from the inner part of the blister roof.

Differential Diagnosis

Atopic Dermatitis

May be clinically indistinguishable from tinea pedis.
KOH examination negative; fungal culture no growth.
An atopic predisposition or other atopic symptoms may be present.

Contact Dermatitis

Occurs most often on the dorsum of the feet.

Palmoplantar Psoriasis

Scale tends to be quite thick.
Psoriasis may be present elsewhere on the body.

Dyshidrotic Eczema

May mimic acute vesicular tinea pedis.
KOH examination negative; fungal culture no growth.
Is usually very itchy.

Management

Type 1: Interdigital

For acute oozing and maceration, Burow solution (1% aluminum acetate or 5% aluminum subacetate) wet dressing compresses applied for 20 minutes, two to three times daily may be helpful.
Broad-spectrum topical antifungal creams such as ketoconazole 2% (Nizoral), ciclopirox (Loprox), or clotrimazole 1% (Lotrimin) are applied to affected areas especially in the interdigital web spaces once or twice daily. (See Table 18.1.)

Type 2: Chronic Plantar

Chronic tinea pedis is the most difficult type of tinea pedis to cure, because topical agents do not effectively penetrate the thickened epidermis.
Treatment generally requires oral antifungal agents such as the following:
Terbinafine (Lamisil) 250 mg once daily for 30 days or longer, if necessary.
Itraconazole (Sporanox) 200 mg once daily for 30 days or longer, if necessary.
Fluconazole (Diflucan) 150 to 200 mg once daily for 4 to 6 weeks, if necessary.

Type 3: Acute Vesicular

Treatment is similar to that of type 1, although systemic as well as topical antifungals may be necessary.

Infection

Secondary infection may be treated with “bleach baths”, topical antibiotics, or, if necessary, oral antibiotics.

Prevention

Prevention consists of maintaining dryness and decreasing friction and maceration in the area by
- using a hairdryer set on “cool” after bathing to dry the feet and interdigital web spaces.
- daily application of an OTC absorbent powder, such as Zeasorb-AF that contains miconazole as an active antifungal ingredient applied after the eruption clears to prevent recurrence.

SEE PATIENT HANDOUTS “Athlete's Foot (Tinea Pedis)” and “Burow solution” IN THE COMPANION eBOOK EDITION.

Helpful Hints

A KOH examination of the scale should be performed to confirm the diagnosis of tinea pedis and to rule out its clinical mimickers dyshidrotic eczema, foot eczema, or plantar psoriasis.
When there is a scaly rash on the palms, the feet should always be examined.
If a child younger than 12 years of age has what appears clinically to be tinea pedis, it is more likely to be another skin condition, such as eczema.
When the diagnosis at initial presentation is in doubt, a potent topical steroid may be applied—for a week or so—to relieve the acute itch and burning. The resultant anti-inflammatory effect of the topical steroid also helps to increase the yield of obtaining organisms on KOH examination or culture.
To increase positive yields, KOH examination or fungal cultures should be obtained only after the patient has not applied any topical corticosteroid or antifungal therapy for at least 24 to 48 hours.

Points to Remember

A common error is to automatically assume that every scaly rash on the feet is fungal in origin and mistakenly treat with topical antifungal preparations alone or in combination with topical steroids as a “shotgun” approach. Careful observation and a positive KOH examination or culture reveal the true nature of the problem. This caveat also applies to tinea cruris (see the following section).
Dyshidrotic eczema and acute vesicular tinea pedis can look exactly alike. The diagnosis should be confirmed by KOH examination of scrapings from the lesions.

SEE PATIENT HANDOUTS “Athlete's Foot (Tinea Pedis)” and “Burow solution” IN THE COMPANION eBOOK EDITION.

Tinea Cruris (“Jock Itch”)

Basics

Tinea cruris is a common infection of the upper inner thighs that most often occurs in postpubertal males.
It is generally caused by the dermatophytes T. rubrum and E. floccosum.
In contrast to candidiasis (see later) and lichen simplex chronicus, it generally spares the scrotum.

Pathogenesis

Tinea cruris often begins after repeated vigorous physical activity that results in excessive sweating.
The infecting fungus is usually the patient's own tinea pedis or other fungal infection.
Obesity, diabetes, and immunodeficient states predispose to tinea cruris.

Clinical Manifestations

Lesions are typically bilateral, fan-shaped, annular, or semiannular scaly patches with central clearing and a slightly elevated scaly “active border” (Fig. 18.7).
Lesions may involve the upper thighs, the crural folds, and possibly extend to the pubic area and buttocks.
Characteristically, spares the scrotum and penis.
Typically lesions are pruritic, or can cause “burning,” or be irritating.
Frequently, the patient also has tinea pedis.

Diagnosis

A positive KOH examination or fungal culture is found most easily by sampling from the “active” border of lesions.

Differential Diagnosis

All the following are KOH negative and will have no growth on fungal culture.

Lichen Simplex Chronicus (Eczematous Dermatitis)

Lichenification is present.
Often involves the scrotum.

Inverse Psoriasis

Scrotal and inguinal involvement.
Lesions are confluent (no central clearing).
Although not always present, the identification of lesions consistent with psoriasis in other locations is useful.

Candidiasis (see below in this chapter)

“Beefy” red appearance.
Often involves the scrotum.
Satellite pustules may be apparent.
KOH positive for budding yeast; positive candidal culture.

Also consider:

Intertrigo
Irritant Dermatitis (e.g., Diaper Dermatitis in Adults)
Erythrasma
Rarely, Extramammary Paget Disease

Helpful Hint

A common mistake that many clinicians make is to prescribe combination antifungal corticosteroid products (e.g., Lotrisone) for the treatment of common fungal skin infections without confirming the diagnosis. Steroid atrophy may result from the potent corticosteroid in this product.

Point to Remember

In males, tinea cruris spares the scrotum, distinguishing it from candidal intertrigo which often involves scrotal skin.

SEE PATIENT HANDOUT “Tinea Cruris (Jock Itch)” IN THE COMPANION eBOOK EDITION.

Management

Topical antifungal creams, applied once or twice daily, are often effective in controlling, and sometimes curing, uncomplicated localized infections. Over-the-counter (OTC) preparations of miconazole (Micatin), terbinafine (Lamisil), and clotrimazole (Lotrimin) are readily available (see Table 18.1).
For severe inflammation and itching, a mild OTC hydrocortisone 1% preparation or a moderate-strength prescription topical steroid such as hydrocortisone valerate 0.2% (Westcort) may be used for 4 to 5 days for symptomatic relief.
Systemic antifungal therapy may be necessary in cases that do not respond to topical therapy and in cases of chronic recurrent tinea cruris, particularly in immunocompromised patients.
Prevention is aimed toward decreasing wetness, friction, and maceration by
- using an absorbent powder such as Zeasorb-ANTIFUNGAL.
- Drying the area with a hairdryer after bathing.
- Wearing loose clothing, that is, briefs are less frictional than boxer shorts.

Tinea Corporis (“Ringworm”)

Basics

Tinea corporis is commonly referred to as “ringworm,” by laypersons and many in the health care community to describe practically any annular or ringlike eruption on the body. In fact, there are many nonfungal conditions that assume an annular “ringworm-like” configuration such as granuloma annulare, erythema multiforme, erythema migrans (seen in acute Lyme disease), and figurate erythemas such as urticaria.
Referred to as tinea faciale when located on the face, tinea corporis is most often acquired by contact with an infected animal, usually kittens and occasionally dogs. It may also spread from other infected humans, or it may be autoinoculated from areas of the body that are infected with tinea such as tinea pedis or tinea capitis.
Due to close skin-to-skin contact, wrestlers can frequently transmit tinea corporis; when this occurs it is called tinea gladiatorum.
M. canis, T. rubrum, and T. mentagrophytes are the usual pathogens.

Clinical Manifestations

Lesions are generally annular or semi-annular with progressive peripheral centrifugal enlargement and central clearing. Odd gyrate or concentric rings may appear (Figs. 18.8-18.10).
The scaly, “active border” may sometimes be pustular or vesicular.
Lesions are single or multiple and may be pruritic or asymptomatic.
Majocchi granuloma is a follicular, deep form of tinea corporis. It may result from inappropriate therapy, such as topical steroids, or from shaving that can drive the fungi into hair follicles.
If multiple lesions are present, their distribution is typically asymmetric.
Lesions are found most often on the extremities, face, and trunk.

Diagnosis

Diagnosis is confirmed by a positive KOH (see Figs. 18.11 and 18.12) examination from the leading edge of a lesion or a fungal culture (it is especially easy to find hyphae in those patients who have been previously treated with topical steroids).
A history of a newly adopted kitten or contact with an infected person may provide very helpful information.

Differential Diagnosis of Annular Lesions

Urticaria

Unlike tinea corporis, scale is absent.
Lesions are evanescent and migratory, lasting less than 24 hours.

Granuloma Annulare.

Scale is absent.

Acute Lyme Disease (Erythema Migrans)

Target-like appearance.
Erythema with no scale.
Self-limiting.

Atopic Dermatitis

Scale is often dry and is present uniformly on the entire surface of the lesions.
Lichenification may be present.

Psoriasis

Scale is silvery white and is present uniformly on the entire lesion.
Lesions are well-demarcated and symmetrical in distribution.

Erythema Annulare Centrifugum

A trailing rim of scale is often evident in the superficial variant of this disorder.

Also consider:

Subacute Lupus Erythematosus
Mycosis Fungoides (Cutaneous T-cell Lymphoma)
Erythema Multiforme

Management

First-line treatment is with a topical antifungal agent that is applied to the affected areas twice daily until the eruption has resolved (see Table 18.1).
Systemic antifungal agents (see the earlier discussion of tinea cruris) are sometimes necessary when multiple lesions are present or if infection is present in areas that are repeatedly shaved, such as men's beards (tinea barbae) or, especially, women's legs, in which granulomatous lesions (Majocchi's granuloma) may appear.
If pets appear to be the source of infection, they may also need antifungal treatment after evaluation by a veterinarian.

Positive KOH Examination

Helpful Hints

Tinea corporis is very often misdiagnosed and treated with topical steroids which results in a masking of the typical clinical features and is appropriately called “tinea incognito” (Fig. 18.13).
Tinea incognito is less red and scaly and oftentimes pustular. A high index of suspicion and thorough history is required to make the diagnosis. A KOH and fungal culture will be positive.

Points to Remember

Inquire about sports activities, such as wrestling.
Not all rings are “ringworm.”

Onychomycosis (Tinea Unguium)

Basics

The term onychomycosis refers to an infection of the fingernails or toenails caused by various fungi, yeasts, and molds. In contrast, the term tinea unguium refers specifically to nail infections caused by dermatophytes.
Onychomycosis is uncommon in children, but its prevalence increases dramatically with advancing age, with prevalence rates as high as 30% in those of 70 years and older.
Many patients who have toenail onychomycosis will also have chronic tinea pedis.
The major causes of onychomycosis are as follows:
- Dermatophytes: E. floccosum, T. rubrum, and T. mentagrophytes
- Yeasts, mainly Candida albicans
- Molds, such as Aspergillus, Fusarium, and Scopulariopsis species

Clinical Variants

Distal subungual onychomycosis (Fig. 18.14) accounts for more than 90% of all cases of onychomycosis. It is usually characterized by the following:
1. Nail thickening and subungual hyperkeratosis (scale buildup under the nail)
2. Nail discoloration (yellow, yellow-green, white, or brown)
3. Nail dystrophy
4. Onycholysis (nail plate elevation from the nail bed)
Distal subungual onychomycosis is frequently associated with chronic palmoplantar tinea (i.e., “two feet, one hand” variant of tinea [see above in this chapter]).
In superficial white onychomycosis (Fig. 18.15), the fungus is superficial.
Proximal white subungual onychomycosis (Fig. 18.16) may be seen in persons with human immunodeficiency virus (HIV) infection.
Aside from footwear causing occasional physical discomfort and the psychosocial liability of unsightly nails, onychomycosis is usually asymptomatic.
Onychomycotic nails may infrequently act as a portal of entry for more serious bacterial infections of the lower leg, particularly in patients with diabetes.

Diagnosis

A positive KOH examination or growth of dermatophyte, yeast, or mold on culture is diagnostic.

Differential Diagnosis (also see Discussion in Chapter 22: Diseases and Abnormalities of Nails)

Psoriasis of the Nails

May be indistinguishable from, or coexist with, onychomycosis.
Usually evidence of psoriasis is found elsewhere on the body.
KOH examination is generally, but not always, negative.
Characteristic nail pitting and a yellowish brown discoloration, known as “oil spots,” may be present.

Chronic Paronychia

Seen in patients with an altered immune status (e.g., diabetic patients) and in people whose hands are constantly in water.
Erythema and edema of the proximal nail fold are noted.
Absence of cuticle.

Pseudomonas Infection of the Nail (Green Nail Syndrome)

Onycholysis with secondary bacterial (pseudomonas) colonization.
A distinctive green coloration is apparent.
Usually found in women with long fingernails.

Management

Media attention has brought scores of patients to their health care providers to have their unsightly nails treated with the oral antifungal agent terbinafine (Lamisil). Lamisil is now the first-line treatment for onychomycosis, replacing griseofulvin, which is less effective and is associated with a high recurrence rate (Table 18.1).

Oral Therapy

Important factors to consider before starting oral therapy:

Diagnostic confirmation by KOH examination or fungal culture
Patient motivation and compliance
Family history of onychomycosis
Patient's age and health
Drug cost
Possible drug interactions and side effects (see Table 18.1)

Terbinafine (Lamisil) Tablets

It is fungicidal, especially against dermatophytes.
Long-term cure rate is probably no greater than 40% to 50%.
Side effects are infrequent. However, baseline liver function tests are performed, and the tests are repeated in 4 to 6 weeks.
Terbinafine is an inhibitor of the CYP450 2D6 isozyme. Drugs predominantly metabolized by the CYP450 2D6 isozyme include the following drug classes: tricyclic antidepressants, selective serotonin reuptake inhibitors, beta blockers, certain antiarrhythmics, and monoamine oxidase inhibitors. Careful monitoring is necessary in patients who are also taking these medications and may require a reduction in dose of terbinafine.
This drug has a reservoir effect. Because it persists in the nail for up to 4 to 5 months, there is no need to wait until the nail appears clinically normal as there is continued clearing even after cessation of therapy.

Dosage

Adults: 250 mg/day for 6 weeks for fingernails; 250 mg/day for 12 weeks for toenails.
Alternatively, pulse dosing with 250 mg/day for 1 week monthly for 4 months.
Children: weight 20 to 40 kg: 125 mg/day; weight more than 40 kg: 250 mg/day for 6 to 12 weeks.

Itraconazole (Sporanox) Capsules

Less common treatment option for onychomycosis.
This is a broad-spectrum fungistatic agent.
The primary drawback to the use of this drug is the risk for significant drug interactions.
Long-term cure rate is probably no greater than 40% to 50%.
Side effects are infrequent. However, liver function tests should be performed at baseline and repeated in 4 to 6 weeks.
This drug also has a reservoir effect.

Dosage

200 mg/day for 6 weeks for fingernails; 12 weeks for toenails.
Alternatively, pulse dosing with 200 mg twice daily, taken with full meals, for 7 days of each month (3 months for fingernails, 4 months for toenails).

Fluconazole (Diflucan) Tablets

This is a broad-spectrum fungistatic agent.
It is more extensively used in patients with HIV infection.
It has fewer drug interactions than itraconazole.
Side effects are minimal. Liver toxicity must be monitored if the drug is used long term.

Dosage

50 to 400 mg daily for 1 to 4 weeks or 150 mg once per week for 9 to 10 months

Other Treatment Methods

Surgical ablation of nails is rarely indicated and is generally ineffective.
Laser treatment of onychomycosis can require extensive debridement but may be effective in those who choose not to have oral therapy.
Carmol 40 Gel, containing 40% urea, a keratolytic agent, is applied once daily to thickened nails and used in conjunction with topical antifungal agents to aid penetration.
Penlac Nail Lacquer Topical Solution (ciclopirox 8%) is a nail lacquer often used in conjunction with oral antifungal agent or alone for the prevention of recurrent infection.
Amorolfine nail lacquer is approved for sale in Australia and the United Kingdom, but not in the United States or Canada.
Newer FDA approved topical agents such as efinaconazole 10% solution (Jublia) and tavaborole 5% solution (Kerydin) may prove to be viable alternatives to oral treatment for onychomycosis. Both require daily used for 48 weeks.

Helpful Hints

The following important questions must be answered before oral therapy is prescribed:
1. Patient's age and health status.
2. How much does the nail disease affect the quality of life of the patient?
Risk versus benefit should be evaluated before treating a condition that is often primarily cosmetic in nature.

Points to Remember

Onychomycosis should be confirmed with a positive KOH test or culture before initiating oral therapy.
Treatment with the newer systemic antifungal agents is expensive and not always curative.
Fingernail onychomycosis should prompt inspection of toenails and feet.
A patient with a family history of onychomycosis is less likely to have a successful treatment outcome than a person without such a history.

Outline
Tinea Pedis (“Athlete's foot”)
Tinea Cruris (“Jock Itch”)
Tinea Corporis (“Ringworm”)
Onychomycosis (Tinea Unguium)

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