Beyond soil and pets: Nannizzia gypsea causing kerion in a child.

Abstract

Nannizzia gypsea (formerly Microsporum gypseum) is a geophilic dermatophyte that rarely causes human infection. We report an 8-year-old boy presenting with a tender, edematous scalp lesion with pustules and alopecia for six weeks. Initially misdiagnosed as a bacterial furuncle, mycological examination of plucked hairs revealed hyaline septate hyphae, and culture on Sabouraud's agar showed powdery buff colonies with brown reverse pigmentation. Lactophenol cotton blue mount demonstrated fusiform, thin-walled macroconidia with 4-6 septa. Molecular identification (ITS sequencing) confirmed Nannizzia gypsea with 100% homology. The patient was treated with oral terbinafine for four weeks, resulting in complete resolution without recurrence. This case is notable for the absence of soil or pet exposure, highlighting the diagnostic challenges of kerion due to geophilic species. Early mycological confirmation enables targeted therapy, prevents mismanagement, and supports antifungal stewardship.