The pathogene's role importance of the microsporidia in nature is considerable. The human being, easily in contact, presents clinical manifestations only with some of them and in a very occasional manner. The increased frequency of the immunodepression has permitted to describe recently a new protozoon, Encephalitozoon intestinalis (alias Septata intestinalis) of the family of the Glugeidae and the human illness of which it is the agent. This parasitose is interesting to be presented because of its rarity and its circulation to organs far from one another. The diagnostic has been done thanks to the only optic microscope and confirmed from its visible efficacity of one cure of albendazole. The pyrimethamine could present a relative efficiency on a relapse of the sinusitis.