SUPERFICIAL FUNGAL INFECTIONS Flashcards
PITYRIASIS VERSICOLOR
Superficial fungal infections arise from pathogens that’s restricted the stratum corneum.
PITYRIASIS VERSICOLOR is from Malassezia spp, Lipophilic yeast. A chronic benign superficial cutaneous fungal infection
Malassezia restricta has been implicated in causes of Dandruff (Seborrheic Dermatitis)
Infection can arise at any age but occurs mainly during adolescence (when the sebaceous glands are more active and you sweat heavily)
RISK FACTORS
Genetic predisposition
Warm humid environment
Immunosuppression
Malnutrition
Cushing disease
CLINICAL FEATURES
—Abnormal pigmentation, serpentine hypo or hyper pigmented macules. (Rarely on the scalp, face or genitalia)
—Pruritus and positive fam hx
— Fungemia in infants receiving TPN
— Folliculitis
DIAGNOSIS
KOH examination of skin scrapping confirms diagnosis (cigar-butt hyphae)
Examination of affected areas with a Wood’s lamp light (yellow to yellow green fluorescence)
Findings of spores with short mycellium referred to as ‘spaghetti and meatball’
Histology
Detected by hematoxylin and eosin, PAS or Methenamine silver staining
MANAGEMENT
goal of treatment is not to eradicate Malassezia fromthe skin but to reduce the cutaneous population to commensal levels
disease is non contagious and leaves no permanent scaring or pigmentary change
Initially with topical agent; selenium sulphide, azoles and allyamine antifungals.
Topical imidazoles, e.g. clotrimazole, miconazole, econazole and ketoconazole in various formulations (creams or shampoos, lotions)
Oral azoles for recurrences
Ultraviolet therapy, to induce maturation of existent melanosomes and accelerate repigmentation
BLACK PIEDRA
Piedra means stone in spanish. Fungal infection of the hair shaft caused by Piedraia Hortae.
Occurs only in man and monkeys and occurs in all ages but mostly the young
CLINICAL FEATURES
Gritty nodules on hair shaft recognized as metallic sound when brushing the hair. It usually affect the scalp hair
Hair breakage
May also present as purpuric or necrotic cutaneous papules and nodules in immuno-compromised
DIAGNOSIS
Microscopic examination of hair shaft nodules in 10-15% KOH.
Tightly packed and pigmented hyphae, asci, and ascospores seen attached to the hair shaft
Culture
P. hortae grows slowly on SDA. It is cultured in asexual phase and microscopy reveals septate hyphae and chlamydospores.
Histology
MANAGEMENT
Oral terbinafine
Shaving/ cutting of hair
topical antifungal agent
WHITE PIEDRA
White piedra most usually affects pubic hair, axillary hair, beards, moustache, eyebrows and eyelashes
Aetiology
—Trichosporon spp.
CLINICAL FEATURES
Lightly pigmented, loosely attached nodules around hair shaft
Breakage of hair
DIAGNOSIS
Direct microscopy of hair shaft nodules with 10-15% KOH
Fungal culture- difficult to culture
Molecular identification
Histology
MANAGEMENT
Topical Antifungals
2% Selenium Sulphide
TINEA NIGRA
An uncommon superficial fungal infection that causes brown to black painless patches on palms and soles
Aetiology
Hortaea (Exophialla ) werneckii
CLINICAL FEATURES
Generally asymptomatic.
Brown to black painless macules on palmar aspects of hand or/ and plantar surface of foot or skin of neck/ chest
may expand over time
May be single or multiple lesions with clearly demarcated borders
No erythema, no induration
DIAGNOSIS
Skin scrapings taken from edge of lesions
Direct microscopy with20% KOH shows mycelium with hyphae, brown or yellow in colour and septate
budding yeast cells
Fungal culture at 25°C on SDA shows wet, brown colonies.
Histology
PAS positive, septate hyphae in stratum corneum
MANAGEMENT
Topical antifungal e.g. ketoconazole
Selenium sulphide shampoo
Repeated topical application of keratolytics may decrease pigmentation
CUTANEOUS MYCOSIS (DERMATOPHYTOSIS)
Most common skin infections worldwide
Caused by Dermatophytes (Fungi that only infects Keratinized tissue) i.e Skin, hair and Nails
Does not cause life-threatening or debilitating disease, but cost of management is high
(All Tinea, Qualified by site involved)
Tinea Capitis - head
Tinea Corporis - body
Tinea Ungum and Magnum - Nails of leg and hand
Tinea Barbae - Beard
Tinea Pedis - foot
Tinea Cruris - Genitalia
Aetiology
genera; Microsporum, Trichophyton and Epidermophyton cause disease
Trichophyton spp. infect hair, skin, or nails
Microsporum species infect only hair and skin
E. floccosum infects the skin and nails but not the hair
RISK FACTORS
Warmth
Moisture
Specific skin chemistry
Composition of sebum
Youth
Organism load
Genetic predisposition
Immunocompetence
Condition of exposed skin surface
Nutritional status
TINEA CAPITIS
CLINICAL MANIFESTATION
May present as follows;
Gray patch
Black dot
Fungating exophytic masses
GRAY PATCH
-Most common in children because of lack of flora and fungistatic sebum
-It is contagious
-Dull grey patches of alopecia, scaling, and itching.
Microsporum species
-Produce chains of spores that form sheath around hair shaft (ectothrix)
BLACK DOTS
-Infected hair becomes weakened and breaks off at skin surface
-Gives appearance of black dots
-Spores are produced within hair shaft (endothrix)
Causative agents include; Trichophyton
FUNGATING EXOPHYTIC MASS
—Kerion: Thick plaques of boggy skin resulting from inflammatory and hypersensitivity reaction with superimposed bacterial infections
Microsporum canis
—Favus: Acute inflammatory reaction of hair follicle results in crust formation (scutula) around the follicle. Hair loss occurs in a honey comb destruction pattern.
Trichophyton schoenleinii
TINEA CORPORIS & TINEA BARBAE & TINEA MANUUM ET UNGUIUM
CLINICAL MANIFESTATION
Usually seen on exposed skin of trunk and extremities
Tricophyton spp
Characterized by annular, plaques on glabrous skin with scaly clearing centre surrounded by spreading haemorrhagic border
T.BARBAE
Ringworm affecting beards and necks
Trichophyton spp
Presents as erythema, Pruritus and Pustules
TINEA MANUUM
-Fungal infection of palms and finger webs
-Mostly involves one hand
-Scaling and erythema
TINEA UNGUIUM
-Nail involvement in dermatophytosis
-Begins at lateral and distal edge of nail plate with resultant paronychial inflammation
-Progresses to cause nail thickening, separation from nail bed, discolouration, brittling and dystrophy
T. rubrum, T.mentagrophytes.
TINEA CRURIS & TINEA PEDIS
T.CRURIS
-Serpiginous lesions with enlarging vesicular margins of groin (jock itch)
-Epidemics occur in soldiers, athletes and ship’s crew where fomites and clothing are shared
(Epidermophyton floccosum)
T.PEDIS
-Athlete’s foot
-Chronic infection of toe webs and plantar surface organism prefered site because it is highly keratinized.
May present as;
1.Toe web scaling
2.Fissuring
3.Maceration
4.Scaling of soles and lateral surface
5.Erythema
6.Vesicles
7.Pustules
8.Bullae
9.Pain, pruritus and ulcers with secondary bacterial infection.
DIANOSIS
Specimens
Hair clippings
Skin scrapings
Skin biopsy
Direct microscopy with 20% KOH
Characteristic hyphae or arthrospores are seen.
Wood lamp examination
Brilliant yellow to green flourescence of M. canis and M. audouinii
False positives in oily seborrheic conditions
Fungal culture
Most accurate
Incubation at 25°C
Some species require specific nutrients e.g nicotinic acid and thiamine.
1-3 weeks incubation at room temperature 25°C
Grown on SDA + Cycloheximide or chloramphenicol.
Appearance of colony and microscopic examination on lactophenol cotton blue aids specie identification
ELISA
Serodiagnosis
Research
High sensitivity and specificity
Histology
superficial inflammatory infiltrates
Neutrophils in stratum corneum, septate branching hyphae may also be seen.
PAS and GMS may aid in diagnosis.
Nucleic acid amplification test
TREATMENT
Thorough removal of infected and dead epithelial structures
Topical antifungals
Miconazole
Terbinafine
Clotrimazole
Ketoconazole
Tolnaftate
Econazole
Applied for 2-4 weeks
Continued for 2 weeks after symptom disappear
Short course of Griseofulvin addded for recalcitrant infections
Oral therapy for extensive and recalcitrant disease
Topical therapy alone is ineffective alone for tinea capitis and unguium
Azoles and Terbinafine
Surgical removal of nail
