Microsporum nanum is a pathogenic fungus in the family Arthrodermataceae. It is a type of dermatophyte which causes infection in dead keratinized tissues such as skin, hair, and nails. Microsporum nanum is found worldwide and is both zoophilic and geophilic. Animals such as pigs and sheep are the natural hosts for the fungus; however, infection of humans is also possible. Majority of the human cases reported are associated with pig farming. The fungus can invade the skin of the host; if it is scratched off by the infected animal, the fungus is still capable of reproducing in soil.