Mushrooms

Fungi are ubiquitously distributed, heterotrophic organisms. Fungi form a system of their own with over 100,000 known species. Only a few hundred are known to cause mycoses. Fungi are not plants. Unlike plants, they are not capable of photosynthesis. In this respect, they are dependent on organic materials. Unlike bacteria, fungi are eukaryotes. Their genome is organized in a cell nucleus. The essential structural element in the cell wall of fungi is chitin. In addition, there are polysaccharides such as mannan and glucan.

Fungi reproduce sexually and asexually:

• Fungi with sexual reproductive cycle are called teleomorphic fungi, also Fungi perfecti.
• Fungi that reproduce asexually are also called anamorphic, Fungi imperfecti . Most of the clinically significant fungi fall into the group of Fungi imperfecti.

Spores: The cells used for reproduction are called spores. Asexual reproduction is by sprouting, by disintegration of hyphae into individual fragments. These are called limb spores or arthrospores. Spores that have formed a covered outer wall to protect against desiccation are called chlamydospores (mantle spores).

Conidia: Furthermore, spores are formed on pre-existing hyphae as well as in spore carriers(conidia). The structure and morphology of conidia are used for micromorphological differentiation of fungi. Conidia are classified according to the number of cells they consist of as.

• microconidia (up to 2 cells) or
• as macroconidia.

In most cases, humapathogenic fungi cause only superficial infections of the skin and mucous membranes, since an intact immune system is able to fight off few pathogenic fungi and thus prevent systemic (ivasive) infections. Nevertheless, systemic fungal infections are gaining in importance as immunosuppressive therapies increase. According to clinical aspects can be distinguished:

• Superficial mycoses (dermatomycoses)
• Subcutaneous mycoses
• Systemic mycoses, in which the skin organ may be affected in the context of a septic process.

Dermatomycoses comprise diseases caused by fungal colonization of the skin and its appendages. The pathogens are predominantly dermatophytes. Dermatophytes are keratinophilic fungi. They cause infections superficially; in the stratum corneum as well as in the keratinized skin appendages (hair, nails). Infections of the skin, mucous membranes and nails with Candida yeasts are also classified as dermatomycoses.
Moulds usually secondarily infect already pathologically changed skin. The most important human pathogenic mould genus is Aspergillus (see below Aspergillosis).

1. Mayser P (2010) Mycological training. Almirall-Hermal
2. Mayser P (2018) Mycoses. In: Braun-Falco`s Dermatology, Venerology Allergology G. Plewig et al. (Hrsg) Springer Verlag S 261-297