Skin infections: Erythematous plaques:(Fungal etiology): 1-Dermatophytosis: (Tinea): -Diffused Fungal infections of the Keratinized tissues of the body; Stratum corneum, Skin epidermis, and dermis. -Contagious infection: Direct contact from animals (goats, sheep, camel, cows, horses) to man (Zoophilic). Transfer form one area of the body to another Familial cross infection occurs.

N Clinical presentation of Tinea lesions: -Erythematous Macules, papular lesions; solid raised skin lesions with defined borders (less than 1 cm). -Slowly expanded or enlarged patches in circular erythematous margins; Erythematous plaques where hair has broken off. -Example: Tinea capitis.

n Classification of Tinea according to infected body’s parts: 1-Tinea capitis: Scalp skin and hair. 2-Tinea corporis: Trunk skin and hair and other sites. 3-Tinea cruris: Groin area. 4-Tinea pedis: Foot skin and toenails( Athlete’s foot). 5-Tinea unguium: Brown discoloration at the edge of the nails, thick-soft- irregular nail. Tinea Corporis; Dermatophytosis of skin.

n Mode of transmission of Dermatophytes: -Human to human -direct skin-to-skin contact with an infected person -Geophilic species -Keratin - utilizing soil saprophytes -Object to human: Anthropophilic species; -clothing, bed linens, combs or brushes. -Animal to human : Zoophilic species: -dogs and cats, especially kittens -cows, goats, pigs and horses

Diagnosis of dermatophytosis: 1-Clinically: -Clinical presentation of lesions: itching expanded in a circular erythematous pattern with skin de- Keratinization. -Woods Lamp: Blue-green or others. 2-Laboratory: Clinical specimens: Hair, nail, and skin from lesion’s margins. Microscopy: 1- A 20% potassium hydroxide (KOH) wet-mount preparation. -Skin de-keratinization. 2- A Lactophenol-cotton blue stained preparation. -Fungal stain.

n Causative agents of dermatophytosis: A group of related filamentous fungi with septate hyphae and Macro- and/or Microconidia. 1-Microsporum canis: spindle-shaped Macroconidia. 2-Epidermophyton mentagrophytes. 3-Trichophyton mentagrophytes: -Macro and Microconidia.

n Cultivation of Dermatophytes: - Sabouraud`s dextrose agar (SDA): the standard media for most fungi. Chloramphenicol added to inhibit bacterial growth. Microspora canis Trichophytone mentagrophyte Trichophytone rubrum Therapy: -Itraconazole, or fluconazole to treat Tinea unguium. -Terbinafine for treatment of Tinea capitis, Tinea corporis, Tinea cruris, Tinea pedis.

n Erythematous plaques:(Fungal etiology): 2-Candidiasis: (Skin, Genital area, Mouth). -Causative agent: Usually Candida albicans (dimorphic). -Oral candidiasis (Thrush): -In Immuno-compromised patients: Infants, Elderly, AIDS, Others with defect in immunity -Vaginal candidiasis: -Itching in the genital area. -White, clumpy discharge. -Transfer of infection to sexual partner. -Seen after antibiotic therapy.

n Candidiasis: Oval yeast cells of Candida Germ tube positive test for C.albicans

Subcutaneous Fungal Infection: A-Sporotrichosis: -Caused by Sporothrix schenkii. -Dimorphic fungi: Cigar-shaped conidia at 25C. B-Mycetoma (Madura foot): -Localized skin abscess due to granulomatous infection of dermis and subcutaneous tissue. -Caused by: 1-Pathogenic soil fungi: Madurella mycetomatis. 2-Bacteria: Actinomycetoma: Actinomyces species or Nocardia.

N Madura foot: Clinical presentation and etiology: Actinomyces species: Gram’s positive braching bacilli.

N C-Chromoblastomycosis and Mycetoma:

Superficial Mycosis: 1-Pityriasis Versicolor: It is a superficial chronic infection of stratum corneum. Infection of the keratinized epithelial cells. Causative agent: Malassezia furfur; (a lipophilic yeast organism; Normal flora of skin). Clinical presentation: Hypo- or hyperpignented macules on chest or back.

n Diagnosis: -Skin scraping -Potassium hydroxide (20% KOH) -Positive for short hyphae and yeast cells - Spaghetti and meatballs. -Culture.

n 2-Tinea Nigra: Exophiala werneckii : Infection of Stratum corneum -Black painless patch (Macule) 3-Black Piedra: Piedraia hortae Infections of scalp hair. 4-White Piedra Trichosporon beigelii : Fungal infection of facial, axillary or genital hair.

n Treatment of Superficial Mycosis: -2% salicylic acid -3% sulfur ointments -Whitfield's ointment -Ketoconazole -Piedra -Cutting or shaving the hair -Or apply 2% salicylic acid -Or 3% sulfur ointment -Nizoral shampoo (contains Ketoconazole).

Other skin infections: Necrotic and Ulcerative lesions: 1-Cutaneous Anthrax: Bacillus anthracis infection: -Contaminated animal products. -Forms about 95% of anthrax cases. -Inoculation of skin by spores. -Spore germination. -Development of papule. -Malignant pustule. -Lymph nodes. -Fetal septicemia.

n 2- Primary syphilitic chancre: Treponema pallidum infection. -Inoculation of microbe into skin cracks. -Development of skin ulcer(chancre); within three weeks. -The lesion heals spontaneously, but the microbes spread by blood and lymph.

n 3-Cutaneous Leishmaniasis: -Blood-feeding vector transmission. -Etiology: Leishmania tropica. (Tissue Mastigophora). -Sandfly carry the Promastigotes; the infective stage. -Infection of skin macrophage. -Skin ulceration.

n Parasitic skin infection: 1-Cercarial dermatitis -Direct penetration of larva. -Schistosoma species: -Infective stage : Cercaria. -Skin penetration; Rash. 2- Ancylostoma infection: Infective stage: Filariform larva; skin penetration.

n Viral infection of Skin: Exogenous: -Cutaneous Warts: -Etiology: Papillomavirus; non-enveloped, DS-DNA virus. -Infection of skin epidermis (basal cells). -Viral capsid proteins in stratum corneum. -Cellular proliferation and excess keratin synthesis. -Thickened dead layer of skin with infectious virus.

n Endogenous: -Viral Exanthems (viral-skin rashes): Etiology: 1-Herpes simplex. 2-Herpes zoster. 3-Measles. Chickenpox Herpes Zoster