Tinea capitis due to Microsporum ferrugineum: A case of unusual laboratory finding on direct microscopic examination of infected hairs and skin lesions

Abstract

Tinea capitis is a chronic fungal infection of the scalp occurring commonly in children of school age, especially in developing countries. It is caused primarily by the dermatophyte members of genera Microsporum and Trichophyton. Here we report presence of free-living mycelial stage of dermatophytes, a stage of fungal growth which form in culture medias, around affected hairs and skin scrapings of scalp lesions in a 3-year-old boy presenting with alopecia and multiple scaly, non-erythematous plaques. On direct microscopy examination using 10 % potassium hydroxide, the fungal hyphae and arthrospores were detected in ectothrix form. In addition, we also observed numerous multicellular, thick-walled spindle-shaped macroconidia around hairs and skin scrapings. To our knowledge this is the first study reporting dermatophyte's macroconidia directly seen on clinical samples. Species level identification of the dermatophyte isolate growing on Mycosel™ agar was confirmed by PCR-sequencing of internal transcribed spacer of ribosomal RNA as Microsporum ferrugineum. The patient was successfully treated with systemic itraconazole combined with topical ketoconazole shampoo.

Keywords

• Tinea captitis
• Microsporum ferrugineum
• Unusual laboratory finding
• Macroconidia