Medical mycology deals with the nature and the causes of the diseases occasioned directly (mycoses and allergies) or indirectly (poisoning) by fungi. Mycotoxins are toxic molecules that are present in various moulds. Reference is made to mycetism when a mycotoxin causes poisoning directly, as is the case for instance with Amanita phalloides (Death Cap). Mycotoxicoses are diseases caused by ingestion of foodstuffs in which toxins are released and therefore involves an indirect form of poisoning. The most well-known example is aflatoxicosis caused by aflatoxins produced by Aspergillus flavus. Some moulds can cause allergic syndromes such as extrinsic allergic alveolitis (e.g. cheese washer's lung, maltworker's lung). All these conditions differ from mycoses, which are a parasitic type of infection. This text deals only with mycoses.
The term subcutaneous mycosis means a disease in which the pathogen, an exosaprophyte, penetrates the dermis or even deeper during or after a skin trauma. The lesions gradually spread locally without dissemination to deep organs. However, most fungi which cause subcutaneous mycoses can also occasion deep mycoses in patients with severe underlying abnormalities (via the respiratory tract). Mycologically the pathogens of subcutaneous mycoses have only a few common characteristics and belong to very different taxonomic groups.
Subcutaneous mycoses occur exclusively or predominantly in the tropics. This is related on the one hand to the geographical distribution of the pathogens and the ecological factors that determine their saprophytic growth and sporulation and on the other hand it is also the consequence of the medical underdevelopment in these regions. Imported or indigenous cases are only rarely found in Western Europe.