December 20, 2019
3 min read
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6-year-old girl presents with itchy rash on leg

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A 6-year-old girl presents with a rash on the back of her left leg for the past month. The rash is very itchy.

Michele Khurana
Marissa J. Perman

She has a history of mild atopic dermatitis that is usually managed with emollients. Her family recently got a pet cat. She went to an urgent care center and was prescribed triamcinolone 0.025% ointment. This topical was used twice daily for 3 weeks with some initial improvement, but the rash then worsened (Figure 1).

Can you spot the rash?

Figure 1. Expanding, scaly, annular plaque with raised borders on the left posterior leg and scattered, follicular papules centrally.

Source: Marissa J. Perman, MD

A. Eczema

B. Majocchi’s granuloma

C. Contact dermatitis

D. Psoriasis

E. Bacterial folliculitis

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Case Discussion

Majocchi’s granuloma (correct choice — B) is a granulomatous folliculitis due to a dermatophyte fungus infecting the hair follicle. Dermatophytes are responsible for causing superficial fungal infections of the skin (such as tinea corporis), hair (tinea capitis) and nails (tinea unguium). Trichophyton rubrum and Trichophyton mentagrophytes are the most common pathogens that cause Majocchi’s granuloma, but many other dermatophyte species can also elicit this granulomatous reaction. In children, these infections are most commonly acquired from contact with affected humans or pets.

The classic presentation of Majocchi’s granuloma is scaly erythematous plaques with multiple perifollicular papules and/or pustules. This is frequently seen after topical steroid use on a dermatophyte infection of the skin. Initially, the patient with tinea corporis is often incorrectly diagnosed with an inflammatory dermatosis such as eczema or psoriasis and treated with a topical steroid. Although initial improvement in erythema may be seen, the topical steroid drives the superficial fungal infection deeper into the skin and hair follicles, resulting in a granulomatous folliculitis. Therefore, it is important for the clinician to be able to accurately distinguish between superficial fungal infections and inflammatory skin disease. Clues to the diagnosis of tinea corporis include annular configuration, central clearing, an active raised scaly border and an asymmetric distribution.

Figure 2. Potassium hydroxide wet-mount preparation with arrow pointing to branching hyphae.

Source: Marissa J. Perman, MD

A simple in-office test to determine the presence of dermatophyte is with a potassium hydroxide (KOH) wet-mount preparation. A number 15 blade or glass slide can be used to gently scrape the active border of a suspicious lesion. A cover slip is applied over the skin scrapings, and 10% to 20% KOH is added. The slide should be gently heated, but this is not needed if the KOH media contains dimethyl sulfoxide. If branching septate hyphae are visualized under the microscope, the KOH test is positive for fungus. This patient had a positive KOH preparation, as seen in Figure 2.

Ultimately, the gold standard for diagnosis of a fungal infection of the skin, hair or nails is with a fungal culture. If there is any suspicion for tinea, a fungal culture should be obtained. A toothbrush or wet cotton-tipped applicator can be rubbed over the skin to easily and painlessly obtain a sample for culture.

Tinea corporis can usually be managed with a topical azole or allylamine antifungal agent twice daily for a few weeks’ duration. Combination topical, antifungal, high-potency steroids like clotrimazole/betamethasone dipropionate are not recommended to treat dermatophytoses because they can elicit Majocchi’s granuloma, cause steroid-related side effects such as striae and are expensive. Fungal infections involving the hair follicle (such as Majocchi’s granuloma and tinea capitis) require systemic antifungal therapy because of deeper involvement. Griseofulvin and terbinafine are the two oral antifungal agents that are most commonly used in this setting. These are typically used for a few weeks at a time. It is also important to treat any known afflicted contacts or pets to prevent reinfection.

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Disclosures: Khurana and Perman report no relevant financial disclosures.