Clinical Mycology Lec 2 PDF

Lec (2) SUPERFICIAL MYCOSES Dr.Wifag Rabih Superficial mycoses The term “superficial mycosis” applies to diseases affecting the outer most layer of the skin (stratum corneum) or growing along hair shafts. The most common superficial mycosis is pityriasis Versicolor, causing patches of hypo- or hyper...

Lec (2) SUPERFICIAL MYCOSES Dr.Wifag Rabih Superficial mycoses The term “superficial mycosis” applies to diseases affecting the outer most layer of the skin (stratum corneum) or growing along hair shafts. The most common superficial mycosis is pityriasis Versicolor, causing patches of hypo- or hyper-pigmentation of the neck, shoulders, chest, and back, and caused by lipophilic basidiomycete yeasts of the genus Malassezia. Other superficial mycoses: White piedra: soft, beige nodules on the distal ends of hair shafts (Trichosporon species), Black piedra: small firm black nodules on the hair shaft (Piedraia hortae) Tinea nigra: brown to black stain on the palm of the hand or sole of the foot (Hortaea werneckii.) Malassezia furfur Lipophilic yeast Found as normal flora on the skin Diseases: Pityriasis versicolor Pityriasis folliculitis Seborrhoeic dermatitis; Dandruff Systemic infection Tinea versicolor( Pityriasis versicolor) This is a very common superficial mycosis caused by a lipophilic yeast Malassezia furfur. It is seen in all countries but is particularly common in the tropics with more than 60%of the population infected. The lesion is hypo or hyper-pigmented. Multiple patchy lesions (oval-shaped fine scales) either light in color or brown Typically occurs on the back, neck, chest, and shoulders. Asymptomatic Tinea versicolor Clinical manifestations Maculae White, cream, pink, red, and brown Scale Painless Not itching Tinea versicolor Pityriasis folliculitis There also is Malassezia folliculitis. This is seen in patients who are usually severely ill or in patients after sun exposure. Follicular papules and pustules Back, chest, and upper arms  Sometimes the neck, seldom the face Itchy Pityriasis folliculitis Seborrhoeic dermatitis Change in quantity and composition of sebum increase wax esters Increase in alkalinity of the skin External local factors such as occlusion Seborrhoeic dermatitis Clinical manifestations Erythema and scaling in area with a rich supply of sebaceous glands Scalp, face, eyebrow, ear and upper trunk Lesions are covered with greasy scales Itching is common in the scalp Systemic infection Common among infants as catheter acquired * intravenous infusions of lipid * pneumonia results from emboli from the infected IV catheter Laboratory diagnosis Sampling Skin scraping(sharp-blade instrument) Blood Indwelling catheter tips Wood lamp( producing ultraviolet radiation) 1. Direct: for skin scraping -10%KOH positive for short hyphae and spores( Spaghetti-hyphae and meatballs- yeast-cluster of thick wall around the budding yeastlike cell. Direct examination Culture Culture: For systemic infection Sabouraud Dextrose Agar or sheep blood agar flood with Olive oil Rarely done. Currently no commercially available serology Management and Treatment 1. Topical agent: imidazole  Ketoconazole shampoo 2. Oral treatment Ketoconazole Itraconazole 3. Alternative zinc pyrithione shampoo Selenium sulfide lotion Propylene glycol 50% in water twice daily White piedra Cause by: Trichosporon beigelii Worldwide, tropical or subtropical regions More in temperate zones Superficial cosmetic fungal infection of the hair shaft Affects scalp, axilla, facial and genital hair White piedra Clinical manifestations Common in young adults Nodules: Mucilaginous, white, follicles not affected Irregular, soft, white, or light brown nodules firmly adhering to the hairs 1.0- 1.5 mm in length No pathological changes are elicited. Laboratory diagnosis Sample : hair 1. Direct Microscopy 10% KOH Arthrospores 2. Culture White or yellowish to deep cream colored Smooth, wrinkled, dull colonies with a mycelial fringe Black piedra Piedraia hortae Common in central and south America and south East Asia Disease: Chronic fungal infection of the hair shaft Mostly affects young adults. Epidemic in families Clinical manifestation Does not penetrate the hair follicle Scalp hair: hard black nodules on the shaft Thick part: fungal cells cemented together Thin part: hyphal elements Black piedra Laboratory diagnosis Sample: hair with hard black nodules 1. Direct microscopy 10% KOH Darkly pigmented nodules 2- Culture Primary isolation media( colony are dark, brown- black) Take about 2-3 weeks to appear Black piedra Management and Treatment Shaving or cutting the hair is the treatment of choice Treated by Topical antifungal agents in the form of cream or shampoos are effective; 2% ketoconazole or 2% miconazole shampoo applied once a week for three weeks is effective Oral antifungals such as terbinafine and itraconazole have been used successfully in cases resistant to topical medications. 250 mg of oral terbinafine once daily for 6 weeks Tinea nigra Exophiala werneckii Common saprophytic fungus( soil, compost, humus and on wood) Chronic superficial fungal infection of the palms and soles Brown to black macules( palmar and plantar and other surfaces of the skin Well-defined dark patch with irregular margin, 1-5 cm in diameter on the palm( stained appearance) Tinea nigra 1. Lesion : noninflammatory and non-scaling Both tropics and temperate zones usually female3:1 Predisposing factor: excessive sweating Laboratory diagnosis Specimen: Skin scraping 1. Direct Microscopy ( 10% KOH) Pigmented brown to dark(dematiaceous)septate hyphal elements 2. Culture Sabouraud’s dextrose agar (Budding yeast) Colonies are mucoid, yeast like and shiny black(young yeast) Serology not required for diagnosis Management & Treatment Sulfur soap,SSA, azole Topical treatment Whitfield ointment(benzoic acid compound) Imidazole agent twice a day for 3-4 weeks Thank you