Tinea corporis due to the rare geophilic dermatophyte Microsporum praecox

摘要

A 10-year-old girl suffered from tinea corporis with erythematosquamous and centrifugal growing, sparse itching lesions of her right lower arm. Fluorescence optical BlankophorA (R) preparation from skin scrapings revealed fungal hyphae. On Sabouraud's dextrose agar, the fast growing dermatophyte formed flat, peripheral radiating and convolved colonies with white, slightly yellowish to beige brown stained granular and powdery surface. The reverse side of the colonies was smooth with luminous yellow colour. Microscopically, an attitude of thin-walled spindle-shaped and echinulate (with small spins) and lanceolate macroconidia appeared. The small based macroconidia are raised in the middle and end part, however, pointy at the end ("spearhead"). Three to six or seven across septae are formed. The small piriform microconidia had an orthotropic arrangement. Chlamydospores were also formed. Urease activity was positive. Macromorphologically, Trichophyton (T.) interdigitale (formerly T. mentagrophytes) was suspected. Due to the shape of macroconidia, Microsporum (M.) gypseum and M. fulvum were also considered as possible species identification. Direct uniplex-PCR-EIA of the strains revealed negative results for T. rubrum, T. interdigitale, T. anamorph of Arthroderma benhamiae and M. canis. Sequencing analysis of the ribosomal ITS-region (18 S rRNA, ITS1, 5.8 S rRNA, ITS2, 28 S rRNA) and of the translation elongation factor 1aEuroalpha (tef-1-alpha) gene revealed the dermatophyte species M. praecox. Topical treatment was done using ciclopiroxolamine cream. M. praecox represents a geophilic dermatophyte, morphologically resembling M. gypseum. Horses are often the source of infection. In humans, M. praecox causes tinea corporis and tinea capitis. For oral treatment of dermatomycosis due to M. praecox, griseofulvin and terbinafine can be used.