Superficial Mycoses

Dr. Pendru Raghunath Reddy

SUPERFICIAL MYCOSES The superficial mycoses are usually confined to the outermost

layer of skin, hair, mucosa and do not invade living tissues

Superficial mycoses

• Do not elicit immune response• No discomfort • Cosmetic problems• Limited to stratum corneum

Superficial Mycoses

1. Pityriasis versicolor

2. Tinea nigra

3. Black piedra

4. White piedra

Pityriasis Versicolor

Caused by Malassezia furfur (Pityrosporum orbiculare) lipophilic yeast Found as a normal flora on the skin Rich in sebaceous glands Grows on media supplemented with fatty acids Exist in budding yeast,occasionally hyphal

Diseases : Pityriasis versicolor Pityriasis folliculitis Seborrhoeic dermatitis; Dandruff Systemic infection

Major clinical manifestations:

– Hyper- or hypopigmented of the skin

– Lesions are well-demarcated (white, pink or brownish)

– Fawn-colored macules are the most common presentation

Trunk and upper arms

Rarely on neck and face

http://dermnetnz.org/common/image.php?path=/fungal/img/pitver4.jpg

Pityriasis folliculitis

follicular papules and pustules

back, chest and upper arms

sometimes the neck, seldom the face

Itchy and often appear after sun exposure

Pityriasis folliculitis

Seborrhoeic dermatitis

Changes in quantity and composition of sebum increase in wax esters shift from triglycerides to shorter fatty acid chains

Increase in alkalinity of skin

External local factors such as occlusion

Clinical manifestations:

Erythema and scaling in areas with a rich supply of sebaceous glands

scalp, face, eyebrows, ears and upper trunk

Lesions are covered with greasy scales

Itching is common in the scalp

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Laboratory diagnosis

Specimen: Skin scrapings

Methods:

1. KOH preparation

2. Culture

KOH preparation

Both budding yeast cells and hyphae can be demonstrated

Shows characteristic ‘spaghetti and meatballs’ appearance

•Short fragments of hyphae•clusters of yeast• Spaghetti and meatballs appearance

Culture

M. furfur requires fatty acids for growth, hence is cultured on SDAwith a layer of olive oil

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

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

TINEA NIGRA

• Tinea nigra is an infection of keratinised layer of skin caused by Exophiala werneckii or Cladosporium werneckii

• C. werneckii is a dimorphic fungus that produces melanin

•palmar•brown•no scaling•no inflammation

A well-demarcated brown-black macular lesions which usually occur on the palmar aspects of hands and occasionally the plantar and other surfaces of the skin

Lesions are non-inflammatory and non-scaling

Laboratory diagnosis

KOH preparation

Microscopy of the KOH preparation of skin scrapings collected from the affected part

Typical darkly pigmented yeast-like cells and hyperfragmented hyphae are demonstrated

Culture

Initially colonies are mucoid, yeast-like and shiny black (young yeast)

Abundant aerial mycelia and become velvety, dark olivaceous in colour. (mature mould)

Management & Treatment

Sulfur soap, SSA, azoles

Topical treatment Whitfield's ointment (benzoic acid compound) Imidazole agent twice a day for 3-4 weeks

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Black Piedra

• Black piedra is a superficial infection of the hair caused by Piedraia hortae, a dematiaceous fungus

Clinical Manifestations

Does not penetrate the hair follicle

presence of hard nodules found along the infected hair shaft

Nodules: hard, fusiform, firmly attached to hair shaft

Laboratory diagnosis

Demonstration of nodules containing asci with spindle shapedascospores in 10% KOH mount of the hair

Culture

Management and Treament

Shave or cut the hairs short

Terbinafine Dose: 250 mg a day for 6 weeks

White Piedra

• Infection of the hair caused by yeast-like organism Trichosporon beigelli

• Commonly found in South America, Central and Eastern Europe and Japan

• The hair of scalp, moustache, and beard are commonly affected

• The development of a soft, pasty, cream-colored growth along infected hair shaft characterizes the condition

• The initial growth occurs beneath the epidermis of hair• The infected hair shaft consists of mycelium that rapidly

fragments to arthroconidia

In this picture we see hair with white piedra (Trichosporon beigelii). Note that, when this module is compared with that seen in black piedra, it is not as discrete and lacks the dark coloration. Additionally, this fungus does not produce ascospores. When cultured on Sabouraud’s agar and incubated for 2-4 weeks at room temperature, this fungus produces a rough, membranous, white to light tan colony. Microscopically, the organism produces no characteristic spores.

Laboratory diagnosis

1. Direct Microscopy

Fragmented hyphae that develop into arthroconidia or produce blastoconidia in 10% KOH mount of hair

This is a 4-5 weeks old culture of Trichosporon beigelii grown on SDA agar at room temperature

2. Culture

Grown on SDA with cycloheximideWhite or yellowish to deep cream coloredSmooth, wrinkled, velvety, dull colonies with a mycelial fringe

Management and Treatment

Shave the hairs

Topical: imidazole agent