A Household Microsporum canis Dermatophytosis Suggested by Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry Analysis.

BACKGROUND Microsporum canis is a pathogenic dermatophyte that usually colonizes animals, and secondary infection of humans comes from pets. The infected patients show hair loss with erythema and are diagnosed as having dermatophytosis, but the transmission routes of M. canis from animals to others are sometimes unclear, although they are critical to the treatment of patients and infection control. To identify the pathogens and the transmission routes, morphological observations by microscopes and conventional polymerase chain reaction (PCR) have been used; however, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has recently become a useful tool. CASE REPORT A 4-year-old girl presented with pruritic, erythematous lesions on the head with alopecia. The dermatologists diagnosed dermatophytosis caused by fungal infection, and M. canis was suspected as the pathogen because of the morphologic characteristics. All of her family members subsequently showed similar hair findings and symptoms. The growth of M. canis was also observed in serial cultures, and all strains were confirmed to be identical, but different from the standard strain on MALDI-TOF MS. In this household infection case, abandoned cats were considered to be the origin of M. canis transmission, and the family members finally improved following oral administration of antifungal agents. CONCLUSIONS M. canis should be carefully investigated as the causative pathogen of dermatophytosis secondary to household infection. MALDI-TOF MS appears to be an excellent tool to confirm the transmission routes of the fungal pathogens among infected patients.