Fungal Infections Of Skin 06-07

Fungal infections of the skin

Fungal infections of the skin Superficial mycosis infection confined to the outer most layer of skin and /or hair • • • • •

Pityriasis versicolor Keratomycosis Tinea nigra Black piedra White piedra

Cutaneous mycosis (Dermatophytosis) Infection of the keratinized layer of skin, hair or nail • Trichophyton • Epidermophyton • Microsporum organisms Subcutaneous mycosis Involve deeper skin layers, including muscle and connective tissues

Dermatophytosis Pathogenesis

Cubical

Infection is caused by: • Arthrospores of fungus OR • Keratinous material containing fungal elements Infection needs • Direct contact with infected material • Indirect contact by use of infected items of the patient • Slight skin trauma • Excessive moisture predisposes to dermatophytosis

Rounded

Dermatophytosis (Tinea) Common Clinical Types 1. Tinea Corporis • Infection of skin of trunk, back, dorsum of hand etc 2. Tinea Capitis • Infection of skin of scalp & hair : three forms a) Endothrix o Abundant fungal growth inside hair shaft b) Ectothrix o Spores infect the surface of hair c) Favic o Some mycelia are inside the hair shaft with an air space

3. Tinea Barbae • Infection of beard & moustache area 4. Tinea Manum • Infection of hand (palm & interdigital space) 5. Tinea Unguim • Infection of the nail of hand 6. Tinea pedis (Athlete’s Foot) • Infection of feet or toes (soles, nails & interdigital space) 7. Tinea Cruris • Infection of perineal area

Dermatophytosis (Tinea) Epidemiology According to source of infection 1. Anthropolic • From human to human e.g. E. floccosum 2. Zoophilic • From animal to human e.g. M. canis 3. Geophilic • Spores from soil e.g. M. gypseum

Dermatophytosis (Tinea) Clinical presentation • Most people are asymptomatic • Itching or a rash • A ringworm skin rash o Occurs at site of infection o Has scaly area with redness at outer margin o Appears as irregular rings • On scalp : patches of hair loss • Nails : thickened & brittle

Dermatophytosis (Tinea) Clinical presentation

Ringworm lesions (rashes)

Tinea of the groin (tinea cruris) showing typical circular, erythematous lesions with raised advancing margins.

Dermatophytosis (Tinea) Clinical presentation

Tinea Capitis

Dermatophytosis (Tinea) Clinical presentation

Dermatophytosis (Tinea) Clinical presentation

Athlete’s foot

Dermatophytosis (Tinea) Diagnosis 1. Clinical Presentation 2. Examination under Wood’s light

• Mycotic area of skin or hair produces fluorescent colors 3. Direct Microscopy • Skin & Nail : septated hyphae • Hair : endothrix, ectothrix, favic 4. Culture • On SDA with chloramphenicol & cycloheximide • Dermatophyte Testing Medium (DTM) o Turns from yellow to red o Colony morphology

Dermatophytosis (Tinea) Diagnosis Microscopic morphology from colonies 1. Epidermophyton e.g. E. floccosum Rocket-shape spores with smooth surface 2. Trichophyton e.g. T. rubrum T. mentagrophytes Cylindrical spores wirh smooth surface 3. Microsporum e.g. M. canis, M. gypseum Multicellular spindle-shape

Epidermophyton floccosum

Dermatophytosis (Tinea) Treatment & Prevention Topical Agents • Clotrimazole • Miconazole Systemic Agents (Oral) • Itraconazole • Terbinafine • Griseofulvin : has side effects Prevention of Tinea pedis • Keeping dryness of skin & nails • Drying interdigital spaces with a piece of dry gauze after washing • Powders, open shoes & changing of socks

Superficial Mycosis Pityriasis versicolor (Tinea versicolor) Causative Agent • Malassezia furfur (Pityrosporum) • World-wide 5-50% population affected Pathogenesis & Clinical features • Chronic infection of the upper most horny layer of epidermis • Can affect any site of the skin • Causes depigmentation of skin

Superficial mycosis Pityriasis versicolor (Tinea versicolor) Lab Diagnosis • KOH Preparation • Diagnostic element is Clusters of yeasts with short hyphal fragments called “spagetti & meat balls” appearance Treatment • 1% Selenium sulphide shampoo 7 times in 14 days • Miconazole • Clotrimazole

KERATOMYCOSIS

(=Mycotic keratitis) • Posttraumatic / postsurgical corneal inf. • Etio: Saprophytic fungi (Aspergillus, Fusarium, Alternaria, Candida), Histoplasma capsulatum • Clinical findings: Corneal ulcer

KERATOMYCOSIS • Micr.: Hyphae in corneal scrapings • Treatm.: Surgery (keratoplasty) Topical pimaricin Nystatin Amphotericin B

TINEA NIGRA • Superficial chronic infection of Stratum corneum • Etio: Hortae (Exophiala) werneckii (pigmented) • Frequent in tropical areas • Clinical findings: Brownish maculae on palms, fingers, face

TINEA NIGRA • Micr.:Septate hyphae and yeast cells (brown in color) • Culture: Black colonies • Treatment.: Topical salicylic acid, tincture of iodine

BLACK PIEDRA • Fungal infection of the scalp hair • Etio: Piedraia hortae •

Frequent in tropical areas

• Clinical findings: Discrete, hard, dark brown to black nodules on the hair

BLACK PIEDRA • Micr. Septate pigmented hyphae, and asci; unicellular and fusiform ascospores with polar filament(s) • Culture: Brown to black colonies • Treatment.: Topical salicylic acid, azol cremes

WHITE PIEDRA • • • •

Fungal infection of facial, axillary or genital hair Etio: Trichosporon (yeast) Frequent in tropical and temperate zones WHITE PIEDRA – Clinical findings: Soft, white to yellowish nodules loosely attached to the hair – Micr.: Intertwined septate hyphae, blasto- and arthroconidia – Culture: Soft, creamy colonies – Treatment.: Shaving, azoles