A scaly rash: A diagnosis that rings deep

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Clinical findings

Topical steroids and tinea infections

Application of topical steroids to unrecognized superficial fungal skin infections can have two important clinical consequences. First, it can mask the characteristic scaly, annular appearance of tinea corporis, and may lead to concentric expanding plaques, as seen in Figure 1. This altered morphology, known as tinea incognito, can make the diagnosis more challenging. Second, steroids can modify a patient's local immunologic response. This allows spreading into deeper tissues, and can lead to a dermatophytic folliculitis known as Majocchi's granuloma, as occurred in this patient.^1-4

Etiology

Majocchi's granuloma was first described by Domenico Majocchi in 1883.⁵ Although the exact incidence is not known, it is well described in two populations. Immunocompromised patients, including those taking chronic steroids or with HIV,^6,7 have an increased incidence. In otherwise healthy patients, Majocchi's granuloma results from opportunistic dermatophytic infection, usually in conjunction with the application of topical steroids^2,3 or disruption of the skin barrier. This may come about through routine bumps and bruises in the pediatric population, or secondary to shaving in women.^1,8

Majocchi's granuloma is generally preceded by a superficial fungal infection, which may involve the skin (tinea corporis), scalp (tinea capitis or kerion), feet (tinea pedis), or nails (onychomychosis). ^1,4,5,9 Systemic immunosuppression or topical steroids as mild as 1% hydrocortisone interfere with antifungal activity and local cell-mediated immunity, allowing the fungi to invade deeper tissues.^3,10 Invasion of the hair follicle or adjacent dermal tissue leads to a local suppurative folliculitis or perifolliculitis, and may progress to a granulomatous reaction.¹¹