[Update on microsporidiosis in humans]

The importance of microsporidium as an opportunistic agent in immunocompromised and AIDS patients is reviewed. Five strains of the agent have been described: Encephalitozoon, Enterocytozoon, Nosema, Pleistophora and Septata. The clinical presentation may be as 1) Generalized infections with multisystemic involvement, specially of the central nervous system; 2) Intestinal, that is the most important and frequent localization in man, and that may cause death in AIDS patients; 3) Ocular, that affects cornea, conjunctiva and may extend to paranasal sinuses; 4) Liver and biliary tract infection with granulomatous lesions, hepatic necrosis or sclerosing colangitis and 5) Muscular, affecting skeletal muscle. The diagnosis is difficult and is established finding spores in the affected tissues with light or electron microscopy. Lately, the diagnosis of intestinal microsporidiosis is made looking for faecal spores. The resistant wall of spores hampers treatment. However, good results are obtained with Albendazole in intestinal microsporidiosis.