Superficial Mycoses Lec:2 Dr,Huda

Superficial Mycoses Limited to the outermost layer of the skin 4 Infections 1.Pityriasis versicolor 2.Tinea nigra 3. Black piedra 4. White piedra

Pityriasis Versicolor Malassezia furfur (Pityrosporum orbiculare) is the causative agents. Lipophilic yeast like organism Rich in sebaceous glands Media is supplemented with fatty acids Exist in budding yeast,occasionally hyphal

Pityriasis (tinea) versicolor:a chronic, superficial fungal disease of the skin characterized by well-demarcated white, pink, fawn, or brownish lesions, often coalescing, and covered with thin scales. Text slide.

The colour varies according to the normal pigmentation of the patient, exposure of the area to sunlight, and the severity of the disease.

Lesions occur on the trunk, shoulders and arms, neck but rarely on the face, and fluoresce a pale greenish colour under Wood's ultra-violet light. Young adults are affected most often, but the disease may occur in childhood and old age

350 350. The most common form of the disease seen in Caucasians showing typical hyperpigmented lesions on the trunk.

353. Typical depigmented lesions seen in dark-skinned individuals, for example in Australian Aborigines.

Distribution: World-wide but more common in tropical than temperate climates. Aetiological Agent: Malassezia furfur a lipophilic yeast forming part of the normal flora of human skin.

Seborrhoeic dermatitis and dandruff: Current evidence suggests M. furfur, combined with multifactorial host factors is also the direct cause of seborrhoeic dermatitis, with dandruff being the mildest manifestation. Host factors include genetic predisposition, an emotional component (possible endocrine or neurologically mediated factors), changes in quantity and composition of sebum. Lesions are red and covered with greasy scales and itching is common in the scalp.

Fungaemia M. furfur has also been reported as causing catheter acquired fungaemia in neonate and adult patients undergoing lipid replacement therapy. Such patients may also develop small embolic lesions in the lungs or other organs.

Follicular pityriasis versicolor Lesions are visible around the hair follicles and sebaceous glands. This is a more severe form of the disease

358. Follicular pityriasis versicolor 358. Follicular pityriasis versicolor. Lesions are visible around the hair follicles and sebaceous glands. This is a more severe form of the disease. (Courtesy Dr G. Donald, Adelaide, S.A.).

Laboratory diagnosis Skin scraping & KoH (10%)exam. glycerol and Parker ink solution Under microscope , thick-walled round, budding yeast-like cells and short angular hyphal forms up to 8um in diameter(spaghetti and meat balls). Culture is only needed in cases of fungaemia . Overlay Sabouraud's dextrose agar containing cycloheximide (actidione) with olive oil .

359 359. Skin scrapings taken from patients with Pityriasis versicolor stain rapidly when mounted in 10% KOH, glycerol and Parker ink solution and show characteristic clusters of thick-walled round, budding yeast-like cells and short angular hyphal forms up to 8 um in diameter (ave. 5 um diam.). These microscopic features are diagnostic for the causative agent Malassezia furfur and culture preparations are usually not necessary.

360. Colonies of Malassezia furfur on Dixon's agar 360. Colonies of Malassezia furfur on Dixon's agar. A specialized isolation medium containing glycerol-mono-oleate.

Tinea Nigra Exophiala werneckii Produce melanin black or brown color Grows as yeast  Older hyphae with mycelia and conidia

Tinea nigra Lesion- gray to black macular palms Diagnosis- Skin scrapings with alkali stain Cultures- Sabourauds’s media pigmented yeast and hyphae

Black piedra Piedraia hortae-is the causative agent Clinical feature: presence of hard nodules found along the infected hair shaft Nodules contain asci

Cultures – asexual state - older cultures teleomorphic (asci ,which contain spindle shaped ascospores)

White Piedra Trichosporon beigelii Hair- soft ,pasty,cream colored growth Microscopy : septate hyphae that develop into arthroconidia

White Piedra Grows in media without cyclohexamide Cultures are pasty and white developed deep radiating furrows and become yellow and creamy Microscopic examination septate hypae that develops into arthroconidia

Two forms of piedra Figure 22.15

Superficial mycoses: Trichosporon beigelii Cause of white piedra. Piedraia hortae Cause of black piedra.

Treatment Skin removal of the organism by: 1.Selenium sulfide 2.Thiosulfate 3.Salicylic acid 4.Hyposulfite 5-inhibition of ergosterol by: miconazole

Cutaneous mycoses Skin , hair & nails Evoke cellular immune response Dermatophytes Clinical manifestationsringworm or tinea

Cutaneous mycoses Etiology Microsporum Trichophyton Epidermophyton

General characteristics of Macroconidia and Microconidia of Dermatophytes Genus Macroconidia Microconidia Microsporum Numerous, thick walled,rough Rare Epidermophyton Numerous, smooth walled Absent Trichophyton Rare,thin walled, smooth Abundant

Microsporum

Trichophyton

Cutaneous mycoses Classifications: Anatomic location Tinea pedis Tinea capitis Tinea corporis Tinea cruris Ecologic location Geophilic (from soil) Zoophilic (animal) Anthropophilic (human)

Cutaneous mycoses Keratophilic – use keratin as subject to live ( parasites) Keratinases- invade only keratinized layers

Cutaneous mycoses THE IDENTIFICATION REACTION(ID) Patients infected with a dermatophyte may show a lesion, often on the hands, from which no fungi can be recovered or demonstrated. It is believed that these lesions, which often occur on the dominant hand (i.e. right-handed or left-handed), are secondary to immunological sensitization to a primary (and often unnoticed) infection located somewhere else (e.g. feet). These secondary lesions will not respond to topical treatment but will resolve if the primary infection is successfully treated.  

Diagnosis Diagnosis is based upon: 1. Anatomical site infected 2. Type of lesion 3. Examination with a Woods lamp 4. Examination of KOH-treated skin,hair & nail scales 5-Culture of the organism (Identification based on the conidia).

Differential diagnosis In a differential diagnosis you must consider: 1.     Leprosy 2.     Secondary syphilis 3.     Pityriasis rosea          4.     Psoriasis         5.     Nummular eczema         6.     Lichen planus         7.     Alopecia areata         8.     Trichotillomania           9-     Contact dermatitis.

Treatment Azole (topically & orally) Griseofulvin, or Terbinafine

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