SUPERFICIAL FUNGAL INFECTIONS Flashcards
(15 cards)
What are SUPERFICIAL FUNGAL INFECTIONS?
Superficial fungal infections arise from the pathogen that is restricted to the stratum corneum, with little or no tissue reactions
Superficial and Cutaneous infections are sometimes regarded as superficial
What is PITYRIASIS VERSICOLOR?
Causative organism?
- Malassezia spp.
- lipophilic yeast
- It is a chronic benign superficial cutaneous fungal infection
cutaneous mycobiota
endogenous strains cause infections
One of the most common pigmentary disorders worldwide
Malassezia globosa, Malassezia furfur, or Malassezia sympodialis
Malassezia restricta, have been implicated as causes or contributors to seborrheic dermatitis (dandruff)
It is an opportunistic pathogen being able to convert from saprophytic yeast to parasitic mycelial morphology in the following situations;
Genetic predisposition
Warm humid environment
Immunosuppression
Malnutrition
Cushing disease
Hypopigmentation results from inhibition of Tyrosinase by dicarboxylic acid produced by oxidation of unsaturated fatty acids
CF of PITYRIASIS VERSICOLOR
- Individuals report cosmetically disturbing abnormal pigmentation:
Discrete, serpentine hyper or hypopigmented macules
Usually involves skin over trunk, back, abdomen, proximal extremities, and rarely, scalp face and genitalia. - Pruritus and positive family history in about 20% of cases may be reported
- fungemia in patients—usually infants— receiving total parenteral nutrition
- folliculitis
DIAGNOSIS P. VERSICOLOR
characteristic feature?
- 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 of P. VERSICOLOR
- goal of treatment is not to eradicate Malassezia from the 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
Discuss BLACK PIEDRA
Causative organism?
Occurs in what mammals?
From Spanish word that means “stone”
It is a fungal infection of the hair shaft
The infection is caused by Piedraia hortae
Commoner in the tropics
Occurs only in man and monkeys
Occurs in all ages, young adults most frequently
Clinical features of BLACK PIEDRA
- 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
Discuss WHITE PIEDRA
Causative organism?
White piedra most usually affects pubic hair, axillary hair, beards, moustache, eyebrows and eyelashes
Aetiology
Trichosporon spp.
found in soil, air, water, and vegetative matter
Diagnosis and treatment of BLACK PIEDRA
- 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
Treatment:
Oral terbinafine
Shaving/ cutting of hair
topical antifungal agent
WHITE PIEDRA
Clinical Presentation and diagnosis, treatment
Clinical presentation
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
Treatment
Topical antifungals
2% selenium sulphide
Discuss TINEA NIGRA
Causative organism?
An uncommon superficial fungal infection that causes brown to black painless patches on palms and soles
Epidemiology
Occurs worldwide
Female to male ratio 3:1
Hyperhidrosis is a risk factor
Aetiology
Hortaea (Exophialla ) werneckii
dematiaceous fungus
Saprophytic fungi in soil, humus, and compost in humid tropical and sub-tropical areas with high salinity
Agents are inoculated from contaminated sources into skin at trauma
Organism is nourished by decomposed lipids and requires low pH and high saline environment provided by the skin
TINEA NIGRA
Clinical presentation, diagnosis and treatment
Generally asymptomatic.
Incubation period of 2-7 weeks
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 between affected and unaffected skin
No erythema, no indurationDiagnosis
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
Discuss CUTANEOUS MYCOSIS (DERMATOPHYTOSIS)
Most prevalent skin infection globally
Caused by dermatophytes, fungi that infect only keratinized tissues
skin, hair, and nails
nonviable skin because most are unable to grow at 37°C or inthe presence of serum.
Does not cause life-threatening or debilitating disease, but cost of management is high
Called “Tinea” -resemble the circular holes in garment that was caused by cloth moths
Glabrous skin
Different clinical entities, named according to site involved
DERMATOPHYTOSIS
Aetiology
genera; Microsporum, Trichophyton and Epidermophyton cause disease
Species are geophilic, zoophilic or anthropophilic and are transmitted to humans when exposed to conidia or hyphae in soil, on animals or through direct contact ( shed skin, scales, nails or hair) or fomites (locker rooms, tanning beds, footwears, clothing e.t.c)
As species evolve from geophilic to anthropophilic, they transit from asexual to sexual reproduction
Anthropophilic species cause more human infections than other species and are mild and chronic
Other species cause intense acute inflammatory response that resolves more quickly
They develop enzymes that enable host specificity
The ringworms are qualified by site affected:
Tinea capitis-head
Tinea corporis-body
Tinea unguium-nails
Tinea pedis-foot
Tinea barbae-beard
Tinea mannum-hand
Tinea cruris-genitalia
Genera-Microsporum, Trichophyton,and Epidermophyton
