Microsporum nanum was first described in 1954 by Fuentes, Aboulafia, and Vidal,1 who isolated a "dwarf form" of Microsporum gypseum from a case of tinea capitis (kerion) in an 8-year-old white boy. They classified this organism as M. gypseum var. nanum. Seven months later these same investigators1 isolated a similar strain from a glabrous skin infection in an adult. In 1956 Fuentes2 reported that the 2 isolates previously described had proved to be stable in their gross and microscopic characteristics over a period of 3 years. He then proposed that this organism be considered a new species: Microsporum nanum. Ajello3 now classifies M. nanum as a separate species of Microsporum. The initial case reported by Fuentes et al.1 presented the following findings: 1. The lesion was a kerion. 2. The fungus invaded hair as an endothrix. 3. Infected hairs exposed to Wood's light fluoresced with