Dermatophyte Infection - PDF

Al-Qalam University College Subject: Mycology/theory Department of Medical Laboratory Technology Class: 3 rd stage Dr. Zheeno n. Taha Dermatophyte infection A dermatophyte infection, also known as dermatophytosis or tinea, refers to a group of fun...

Al-Qalam University College Subject: Mycology/theory Department of Medical Laboratory Technology Class: 3 rd stage Dr. Zheeno n. Taha Dermatophyte infection A dermatophyte infection, also known as dermatophytosis or tinea, refers to a group of fungal infections that can affect the skin, hair, and nails. Tinea infections are one of the most common causes of superficial fungal infections around the world, and are distinguished by the area of the body affected. For instance, 1. tinea corporis (i.e. ringworm) affects the arms, trunk, and legs; 2. tinea capitis (i.e. scalp ringworm) affects the scalp and hair shafts; 3. tinea faciei affects facial skin; 4. tinea cruris (i.e. jock itch) affects the groin and inner thighs; 5. tinea pedis (i.e. athlete’s foot) 6. tinea manuum affect the feet and hands, respectively; 7. tinea barbae affects facial hair follicles of bearded individuals. 8. tinea unguium Dermatophyte nail infections are commonly known as dermatophyte onychomycosis. Individuals with decreased immune response, older individuals, and children are at an increased risk of developing a dermatophyte infection. Other general risk factors include diabetes mellitus, poor circulation, and topical corticosteroid use. Organisms Dermatophyte infections are caused by dermatophytes; a group of filamentous fungi that require keratin for growth. Keratin is a family of structural proteins that are found in the hair, nails, and outermost layers of the skin. There are over 20 species of dermatophytes which are classified into three genera: Trichophyton, Microsporum, and Epidermophyton. Despite having the word “worm” in its name, a fungus — not a worm — causes ringworm. The condition gets its name from the raised ring-shaped rash that forms on the skin. Dermatophytes are cutaneous fungi which infect only the keratinized tissues by liberting keratinase enzyme which helps them to invade into keratinized tissue like stratum corneum layer of skin, hair and nail. It is a group of about 40 related fungi that belong to three genra: 1. Microsporum 2. Trichophyton 3. Epidermophyton They are restricted to non-viable skin because most are unable to grow at 37'C Clinical features 1-Tinea pedis (Athletes foot) The toe webs are infected with a Trichophyton species or with Epidermophyton floccosum. Initially there is itching and development small vesicles that rupture and discharge a thin fluid. The skin becomes macerated and cracks appear that are prone to secondary bacterial infection. Nails infection (Tinea unguium, onycomycosis) follows prolonged tinea pedis, nails become yellow brittle, thickened or crumbling. Tinea pedis due to Trichophyton rubrum. Tinea pedis - "athlete's foot". Infection of toe webs and soles of feet Tinea unguium (onychomycosis) - nails 2-Tinea Corpris (Tinea glabrosa, Tinea cruris):(Ringworm): This is a dermatophytosis of non hairy skin of the body that gives rise commonly to the annular lesions of ringworm, with a clearing, scaly center surrounded by a red advancing border that often contains viscles. Dermatophytes grow only within dead keratinized tissue. 3-Tinea cruris Tinea cruris, also known as jock itch, is an infection involving the genital, pubic, perineal, and perianal skin caused by pathogenic fungi known as dermatophytes. 4-Tinea versicolor Tinea versicolor is a common fungal infection of the skin. The fungus interferes with the normal pigmentation of the skin, resulting in small, discolored patches. These patches may be lighter or darker in color than the surrounding skin and most commonly affect the trunk and shoulders. It is superficial skin infection caused by Malassezia furfur. 5-Tinea Barbae (Beard Ringworm) A fungal infection most commonly found in animals like cows causes tinea barbae or beard ringworm in people. The condition causes red, ring-shaped skin rashes. Inflamed areas called kerions can lead to scarring and hair loss. 6- Tinea Capitis (Ringworm of the scalp): Infection beings on the skin of the scalp, with subsequent growth of dermatophyte down the keratinized wall of the hair follicle. Infection of the hair takes place just above the root. Microsporum species grow primarily as a sheath around the hair (ectothrix). Trichophyton species vary in their growth patterns, some invade the hair shaft (endothrix), making it so fragile that it breaks off within or at the surface of hair follicle (black-dot ringworm). In infection of other species, the hair breaks a short distance above the scalp leaving short stubs in a balding. Redness edema, scaling and vesicle formation may be seen. 7- Dermatophytid A dermatophytid reaction is the body's reaction to a dermatophyte (fungal) infection and is a skin eruption that appears on an area of the body that is not the area where the infection first began. A dermatophytid reaction is not actually a type of dermatophytosis. Rather, a fungal infection on one area of the body can cause an allergic skin eruption to appear on another area of the body that is not infected. For example, a fungal infection on the foot may cause an itchy, bumpy rash to appear on the fingers. These eruptions (dermatophytids, also called identity or id reactions) are allergic reactions to the fungus. They do not result from touching the infected area. The eruptions may appear on many different areas of the body at once. The eruptions are typically itchy. They may appear as  Small, fluid-filled spots (on the hands or feet)  Solid bumps  Red, raised patches  Deep, raised, bruiselike areas on the shins  Pinkish red spots that resemble targets  Red, raised swellings (hives) Lab diagnosis 1- 2- 3- 4-