Superficial ~ Subcateneous Infxns Flashcards
Superficial mycoses:
- outer skin layers & hair
Fungi that colonize keratinized outer layers of skin, hair & nails – minimal immune response – non destructive – usually of cosmetic importance
Cutaneous mycoses:
deeper layer of epidermis, possibly nails
Subcutaneous mycoses:
Subcutaneous mycoses: dermis, subcutaneous tissues, muscle & fascia
Pityriasis (Tinea) versicolor
Very common worldwide, caused by yeast Malassezia furfur complex
• Skin scrapings: clusters of spherical yeast cells
Pityriasis (tinea) versicolor; morphology
Transmission
‘• Healthy individuals affected, direct transfer of infected keratinized material form person to person
• Small hypopigmented or hyperpigmented macules (upper trunk, arms, chest, shoulders, face), patches of discoloration, hypopigmented in dark-skinned & pink in light-skinned individuals
Pityriasis (tinea) versicolor;
Diagnosis
• Microscopy of epidermal scales treated with KOH
• The lesions will also fluoresce with a yellowish color upon exposure to a Wood lamp
• Also stains with GMS & PAS. Culture not required
Cutaneous mycoses
Infections by
Infections by dermatophytic fungi (dermatophytosis) or non-dermatophytic (dermatomycoses)
Cutaneous mycoses
’ -Dermatophytosis
Dermatophytosis
• Cutaneous infections usually from Trichosporon spp, Epidermophyton spp & Microsporum spp
• Keratinolytic – infect skin, hair & nails, skin infection is usually limited to epidermis
• Various forms are called tineas or “ringworm” – based on anatomical site infected, classified as:
1. Tinea capitis, scalp, eyebrows 2. Tinea barbae, beard 3. Tinea corporis, smooth body skin 4. T. cruris, groin 5. Tinea pedis, feet 6. Onychomycosis
Cutaneous mycoses
Morphology
• Molds, each genus has specific colony morphology, growth requirements & spore production
• In skin biopsy (GMS, PAS, H/E), all morphologically indistinguishable, septate hyphae or conidia
Cutaneous mycoses
-Epidemiology.
• Transfer of conidia or hyphae, or keratinous material from an infected patient to a susceptible host
• 80-90% of all dermatophytosis are attributed to Trichosporon rubrum & T. mentagrophytes
Cutaneous mycoses
Clinical manifestations
Classic pattern- ringworm
-Ring of inflammatory scaling with a clean centre – if hair areas are involved, patchy alopecia
• If more intense inflammation, = pustules or vesicles
,
Foot & hand cutaneous mycoses
• Mostly adult disease, toe nails more frequently affected than fingernails
• Nails commonly affected & destroyed by fungi – onychomycosis
• Chronic infections – nails become thickened, raised, friable & deformed – T. rubrum most common
Cutaneous mycoses
Diagnosis -
: Dermatophytosis
Hyphae by microscopy of skin, hair, nail scrapings – specimens mounted in KOH
• Culture, skin or nail scraping
Wood lamp
• Lesions from Microsporum spp fluoresce under Wood lamp light
Therapy
• Topical agents if nails are not involved - oral prolonged therapy for onychomycosis
Subcutaneous mycoses
Traumatically introduced into skin, disease involving deeper layers of dermis, subcutaneous
tissue & bones - dissemination to internal organs is extremely rare
Subcutaneous mycoses
Exposure + found where
Exposure is mainly occupational or related to hobbies (gardening, wood gathering, etc.)
Fungi usually of low pathogenic potential & found in soil, wood & decaying vegetation
Chronic, insidious infections, difficult to treat (months or years), hosts usually immunocompetent
Lymphocutaneous sporotrichosis
Chronic subcutaneous infection characterized by nodular & ulcerative lesions, that develop
along lymphatics that drain the primary site of inoculation
• After local trauma at an extremity – initially a small nodule that might ulcerate
• 2-3wks after, linear chain of painless nodules along the course of lymphatics, gradually these too
will ulcerate draining pus from the skin
