These infections, also called mycoses (see MYCOSIS), are common and particularly aﬀect the skin or mucosal membranes in, for example, the mouth, anus or vagina. Fungi consist of threadlike hyphae which form tangled masses or mycelia – common mould. In what is called dermatophyte (multicellular fungi) fungal infection of the hair, nails and SKIN, these hyphae invade the KERATIN. This is usually described as ‘RINGWORM’, although no worm is present and the infection does not necessarily occur in rings. PITYRIASIS versicolor and candidosis (monoliasis – see CANDIDA), called thrush when it occurs in the vulva, vagina and mouth, are caused by unicellular fungi which reproduce by budding and are called yeasts. Other fungi, such as ACTINOMYCOSIS, may cause deep systemic infection but this is uncommon, occurring mainly in patients with immunosuppressive disorders or those receiving prolonged treatment with ANTIBIOTICS.
Diagnosis and treatment Any person with isolated, itching, dry and scaling lesions of the skin with no obvious cause – for example, no history of eczema (see DERMATITIS) – should be suspected of having a fungal infection. Such lesions are usually asymmetrical. Skin scrapings or nail clippings should be sent for laboratory analysis. If the lesions have been treated with topical steroids they may appear untypical. Ultraviolet light ﬁltered through glass (Wood’s light) will show up microsporum infections, which produce a green-blue ﬂuorescence.
Fungal infections used to be treated quite eﬀectively with benzoic-acid compound ointment; it has now been superseded by new IMIDAZOLES preparations, such as CLOTRIMAZOLE, MICONAZOLE and terbinaﬁne creams. The POLYENES, NYSTATIN and AMPHOTERICIN B, are eﬀective against yeast infections. If the skin is macerated it can be treated with magenta (Castellani’s) paint or dusting powder to dry it out.
Refractory fungal infection can be treated systematically provided that the diagnosis of the infection has been conﬁrmed. Terbinaﬁne, imidazoles and GRISEOFULVIN can all be taken by mouth and are eﬀective for yeast infections. (Griseofulvin should not be taken in pregnancy or by people with liver failure or porphyria.) (See also FUNGUS; MICROBIOLOGY.)