Diagnosing Tinea Corporis

By Jacob Mathew, Jr. DO, FACOI, FACP, CHSE, FAWM

Your patient

A 16-year-old boy presents to you for a worsening rash on his inner thigh and abdomen. He first noticed the rash a few weeks into his wrestling team’s summer camp.

Consider tinea corporis

Tinea corporis, also known by the misnomer “ringworm,” is one of many superficial mycotic infections caused by dermatophytes (such as Microsporum canis, Trichophyton mentagrophytes, and Trichophyton rubrum) that invade keratinized tissue such as the skin, hair, and nails. Superficial mycotic infections occur in up to 25% of individuals worldwide¹. Tinea corporis infection manifests as an annular erythematous patch or plaque with a rim of raised scales with central clearance. While tinea corporis involves multiple regions of the body, it may be classified by a different name depending on the areas of involvement (faciei [face], capitis [head], barbae [beard], and cruris [groin], among others). See Table 1 for more information. This discussion will focus specifically on tinea corporis, or fungal infection of the non-hairy body regions (defined as the face, trunk, and extremities).

Tinea corporis is commonly acquired via direct human contact or from an infected pet via fomites. While a patient may present with a single lesion, multiple lesions are common depending on exposure duration and frequency. The initial lesion will start as a pruritic papule that eventually ruptures to form papulosquamous annular lesions with a central clearing. These lesions eventually spread out (up to 5 cm in diameter), extending their peripheral margins, to become vesicles. The most common locations include the neck and back.

TABLE 1 | Variants of dermatophytoses other than tinea corporis2
Image	Name	Most common organisms	Description
	Tinea pedis	Trichophyton rubrum, Trichophyton interdigitale, Epidermophyton floccosum	Most prevalent, affecting 26.5 million Americans yearly, with 70% of patients having this infection at some point in their lives Also called “athlete’s foot” Multiple variants Risk with use of public pools and bathing facilities or sustaining trauma to lower extremities and thus breaks in skin.
	Tinea capitis3	Trichophyton tonsurans, Microsporum canis	Also called “ringworm of the scalp” More often seen in children Three types seen: black dot, gray patch, and favus May be spread by dogs and cats
	Tinea cruris	Trichophyton rubrum	Also called “jock itch” Look for involvement of the medial / upper thighs and groin with excessive moisture and pruritis Males more often affected Look for sparing of the scrotum
	Tinea unguium4	Trichophyton rubrum	Also called “onychomycosis” Can also be caused by Candida species Presents with thick, rough, and discolored nails and may lead to full separation of the nail from the nail bed Test patients for diabetes Often will require prolonged oral therapy, as topical cannot penetrate areas of involvement
	Tinea incognito5	N/A	Prior tinea infection that has changed in appearance secondary to use of a corticosteroid, resulting in a less localized inflammatory appearance Look for a rash that was treated with an over-the-counter steroid and has returned Common areas of involvement include the face and posterior hand

Tinea corporis

If it’s not tinea corporis, what else could it be?

In any patient, including ours above, have a high degree of suspicion for sexually transmitted infections such as syphilis (secondary), as well as other scaly conditions such as pityriasis rosea, psoriasis, tinea versicolor, and nummular dermatitis. Atopic dermatitis can also mimic dermatophyte infections. Differentiation can be made based on the condition’s spread, as dermatophyte infections will often autoinoculate from the initial patch, and also on the central clearance, which is not seen with atopic dermatitis. See Table 2 for more information on the differential diagnosis.

TABLE 2 | Differential diagnosis of annular lesions
Image	Condition	Description
	Tinea corporis	Annular scaling lesions with central clearing Pruritic Multiple variants Risk with use of public pools and bathing facilities or sustaining trauma to lower extremities and thus breaks in skin.
	Atopic dermatitis	Symmetric distribution to flexural creases Chronic and recurrent No central clearing KOH negative
	Plaque psoriasis	Adherent, silvery scales Patient may have underlying autoimmune condition Does not respond to antifungal therapy
	Nummular eczema	Coin-shaped Mostly localized to extremities KOH negative
	Granuloma annulare	Ring eruption Lesions are deeper (dermal) and not superficial (epidermal) No scaling
	Erythema migrans	Associated with a tick bite, often within 30 days Systemic symptoms of fever, myalgias

How am I to diagnose it?

The diagnosis of tinea corporis is confirmed with a potassium hydroxide (KOH) examination of skin scrapings. Direct microscopic examination via 10%-20% KOH is both quick and inexpensive. Given that it can be done at the bedside, it is helpful in confirming clinical suspicion from the provider. Scrapings of loose scales are taken from the margin of the lesion, mounted onto a slide to which KOH is then added, and evaluated under the microscope after a coverslip is applied. Long, smooth, branching, and septal rods / hyphae of uniform width are pathognomonic for fungal infection. (See Figure 2.) While less utilized, culture and antifungal sensitivity testing is possible, but it may take up to 14 days to get a result.

Figure 2 | Skin scrapings with KOH applied as viewed under a microscope

Is tinea corporis associated with any concurrent conditions?

While tinea corporis may seem like a benign fungal infection, consider screening patients for immunocompromising conditions if there is no clear cause for the infection (eg, contact with someone known to be infected, poor hygiene). In patients with human immunodeficiency virus (HIV), presentations may be atypical with the development of abscesses or deeper epidermal infection. Dermatophyte infections in other areas of the body, such as tinea cruris, can extend and develop into tinea corporis in those with HIV⁶.

How can I treat my patient?

A review of treatment options can be found in Table 3. Topical antifungal preparations are often both effective and well tolerated. The goal is for complete eradication of the infection. Depending on the amount of skin involvement, oral antifungals may be considered; however, be aware of associated liver toxicity, which may limit use in select populations. Primary care providers can initiate treatment; however, if there is uncertainty regarding the diagnosis, or if there is treatment failure, referral to a dermatologist can be given.

Mild to moderate skin involvement can be treated with miconazole, clotrimazole, ciclopirox, or ketoconazole administered as a gel, lotion, or cream. The medication is applied to the area of involvement twice a day and continued for at least 7-10 days after the lesions disappear. The typical total duration as a result is often 4-6 weeks. Avoid combining antifungal treatment with topical steroids as it may lead to deeper penetration of the fungal infection and development of resistance. Despite discontinuation of the medication, it will often stay concentrated in the skin and nails for months⁷.

For more extensive involvement where topical preparations would be excessive, systemic (or oral) treatment may be advantageous. Consider testing for immunocompromising conditions such as diabetes mellitus and HIV⁸. Furthermore, hair-bearing sites more often require systemic therapy⁹. As mentioned above, these medications can cause liver toxicity; therefore, avoid using them in patients with known cirrhosis or liver impairment. Liver-associated enzymes (LAEs) such as aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) should be obtained prior to treatment. Consider repeating them at the conclusion of therapy. Patients should be advised to come see you if they notice jaundice or develop abdominal pain while on the medication.

Our patient revisited

For this 16-year-old patient, given the limited area of involvement, I would start with topical therapy. If he does not respond within 1 week into his 6-week treatment, then I would consider oral therapy. Understanding the implications of dermatologic infections in athletes is important to minimize morbidity and prevent transmission. Watch for a forthcoming article on determining return-to-play precautions.

References

1. Sahoo, A. K., & Mahajan, R. (2016). Management of tinea corporis, tinea cruris, and tinea pedis: A comprehensive review. Indian Dermatol Online J., 77-86.
2. Ely JW, R. S., & 90:702-710. (n.d.).
3. Drake LA, D. S., & 34:290-294. (n.d.).
4. Flint WW, C. J., & 98:213-225. (n.d.).
5. TINEA INCOGNITO. (n.d.). Retrieved from American Osteopathic College of Dermatology.
6. WHO. (2014). WHO: Guidelines on the treatment of skin and oral HIV-associated conditions in children and adults. Geneva, Switzerland.
7. Gehris, R. P. (2018). Dermatology. In B. J. Zitelli, S. C. McIntire, & A. J. Nowalk, Zitelli and Davis’ Atlas of Pediatric Physical Diagnosis (pp. 275-330).
8. Trayes Kathryn, S. K. (2018). Annular Lesions: Diagnosis and Treatment. Am Fam Physician, 283-291.
9. Stein, S. (n.d.). Rash. In D. Scott, Symptom to Diagnosis: An Evidence-Based Guide. New York, NY: McGraw-Hill.