Abstract
In this report, we describe five cases of dermatophytosis caused by dysgonic strains of Microsporum canis which occurred in the area of Bilbao (Spain). The clinical presentations and responses to treatment of these infections were apparently similar to those caused by typical strains of this species but the increasing prevalence of dysgonic and other atypical strains of M. canis and the relative stability of the dysgonic morphology are the important features shown in our study. Contact with animals was confirmed by all of the patients, but in only one case was this possible infectious origin demonstrated mycologically. One of the patients, a heroin abuser with AIDS, showed a simultaneous infection with Trichophyton mentagrophytes var. mentagrophytes.