What are tinea infections?

Updated: Apr 27, 2021
  • Author: Mityanand Ramnarine, MD, FACEP; Chief Editor: Jeter (Jay) Pritchard Taylor, III, MD  more...
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Answer

The dermatophytes are a group of fungi that invade and grow in the dead keratin of skin, hair, and nails. Dermatophytes are, by far, the most prevalent of the 3 major classes of superficial infections. [1] Less frequently, superficial skin infections are caused by nondermatophyte fungi (eg, Malassezia furfur in tinea versicolor) and Candida species.

Several species of dermatophytes commonly invade human keratin, and these belong to the Epidermophyton, Microsporum, and Trichophyton genera. They tend to grow outwards on skin, producing a ringlike pattern, hence the term "ringworm". They are very common and affect different parts of the body. Clinically, dermatophytosis infections, also known as tinea, are classified according to the body regions involved.

The type and severity of the host response is often related to the species and strain of the dermatophyte causing the infection. The dermatophytes are the only fungi that have evolved a dependency on human or animal infection for the survival and dissemination of their species. The infection may spread from person to person (anthropophilic), animal to person (zoophilic), or soil to person (geophilic). The most common of these organisms are Trichophyton rubrum, Trichophyton tonsurans, Trichophyton interdigitale and/or Trichophyton mentagrophytes, Microsporum canis, and Epidermophyton floccosum.

Table. Ecology of Common Human Dermatophyte Species. Table reprinted with permission from David Ellis, Bsc (Hons), MSc, PhD, FASM, FRCPA (Hon), Affiliate Associate Professor, The University of Adelaide (http://www.mycology.adelaide.edu.au/mycoses/cutaneous/dermatophytosis). (Open Table in a new window)

Species

Natural habitat

Incidence

E floccosum

Humans

Common

T rubrum

Humans

Very common

T interdigitale

Humans

Very common

T tonsurans

Humans

Common

Trichophyton violaceum

Humans

Less common

Trichophyton concentricum

Humans

Rare

Trichophyton schoenleinii

Humans

Rare

Trichophyton soudanense

Humans

Rare

Microsporum audouinii

Humans

Less common

Microsporum ferrugineum

Humans

Less common

T mentagrophytes

Mice, rodents

Common

Trichophyton equinum

Horses

Rare

Trichophyton erinacei

Hedgehogs

Rare

Trichophyton verrucosum

Cattle

Rare

M canis

Cats

Common

Microsporum gypseum

Soil

Common

Microsporum nanum

Soil/pigs

Rare

Microsporum cookei

Soil

Rare


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