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*Dermatophytes in [[Mycotic skin infections - Pathology#Dermatophytoses|dermatophytosis]]
*Dermatophytes in [[Mycotic skin infections - Pathology#Dermatophytoses|dermatophytosis]]
[[Image: Microsporum canis lesions.jpg|100px|thumb|right|<small><center>''Microsporum canis'' alopecia and scaling lesions (Courtesy of Bristol BioMed Image Archive)</center></small>]]
[[Image: Ringworm dog.jpg|100px|thumb|right|<small><center>Ringworm in a dog (Courtesy of Bristol BioMed Image Archive)</center></small>]]
[[Image: Trichophyton mentagrophytes dog.jpg|100px|thumb|right|<small><center>Trichophyton mentagrophytes in a dog (Courtesy of Bristol BioMed Image Archive)</center></small>]]
*Caused by [[Fungi|dermatophytes]]
**''Microsporum'' - zoophilic
**''Trichophyton'' - geophilic
**''Epidermophyton'' - anthropophilic
*Common in many species, especially cats
*Hot, humid environment predisposes and viable fungi peripherally
*More common in young animals
*Produce proteolytic enzymes to penetrate surface lipid
*Fungal hyphae invade keratin -> break into arthrospores
*Epidermal hyperplasia ([[Skin Glossary - Pathology|hyperkeratosis, parakeratosis, acanthosis]]) and inflammation
*Superficial perivascular dermatitis -> exocytosis (migration through epidermal layers) -> intracorneal microabscesses
*Exocytosis -> folliculitis -> furunculosis
*Highly variable lesions
*Normal -> eruptive nodular -> pseudomycetoma -> onychomycosis
*Grossly:
**Circular or irregular lesion, may coalesce
**Scaly to crusty patches
**Alopecia due to broken hair shafts and hairs lost from inflammed follicles
**Follicular papules and pustules
**Peripheral red ring ('''ringworm''') due to dead fungi in areas of inflammation at centre of lesions and viable fungi peripherally
*Microscopically:
**Perifolliculitis, folliculitis or furunculosis
**Epidermal hyperplasia
**Intracorneal microabscesses
**Septate hyphae or spores may be found in stratum corneum and keratin of hair follicles