Figurate erythematous lesion by Microsporum canis in immunosuppressed patient

Abstract

Dermatophytes are fungi capable of invading keratinized tissues. Isolation of the fungus with the culture is essential to guide the treatment, because there are more resistant species like Microsporum canis. The chronic use of corticosteroids leads to the deregulation of immunity, promoting atypical manifestations of infections. Topical antifungal therapy is often insufficient, requiring systemic medications. We describe the case of a patient undergoing systemic corticosteroid therapy with a large figurate lesion who presented complete response to exclusively topical treatment.

A 39-year-old female patient with systemic lupus erythematosus, on prolonged use of prednisone 40mg/day and hydroxychloroquine 400mg/day, for two months, presented with a round plaque with well-defined borders and extremely figurate center, with areas of scaling and of healthy skin of approximately 10cm in diameter (Figure 1). The direct microscopic examination septate hyaline hyphae; the culture was positive with a white filamentous aspect and a yolk yellow reverse. The microculture showed fusiform macroconidia with more than six cellular divisions, confirming infection by M. canis (Figures 2 and 3). The patient was treated with isoconazole 1% associated to diflucortolone 1%cream for the first 10 days. For the following 20 days, she used isoconazole 1% cream alone, with a complete response to exclusively topical therapy (Figure 4).

Figure 1.

Round plaque with well-defined borders and figurate center

Figure 2.

White, wooly colony with yolk-yellow reverse

Figure 3.

Micromorphology with fusiform macroconidia with more than 6 cellular divisions

Figure 4.

Lesion after treatment

The dermatophytes comprise 3 genera of fungi capable of invading keratinized tissues: Trichophyton, Microsporum, Epidermophyton. Non-specific, cellular and humoral immunologic responses act in an attempt to block infection in the host.¹

Chronic use of corticosteroids causes a deregulation mainly of cellular immunity. Its anti-inflammatory properties mask signs and symptoms of an infection, leading to atypical manifestations such as lesions that are asymptomatic, have a widespread or even figurate distribution, mimicking other conditions such as observed in this case.^2-4

Thus, immunosuppressed patients due to corticotherapy have higher risk of opportunistic infections. The isolation of the fungus in a culture is essential to guide treatment, because there are more resistant as M.canis in imunossupressed patients.⁵ Topical antifungal therapy alone is usually insufficient, and systemic antifungal are commonly required.⁶