Cutaneous Fungal Infections / ©2009 Mark Tuttle
Superficial Skin Infection
Name / Diagnosis/Labs / Symptoms / Pathogenesis / Treatment
Tinea versicolor
Pseudohyphae AND yeast / Caused by Malassezia species
Labs/Microscopy
-  KOH mount for definitive diagnosis
(degrades everything but chitin)
-  Enhanced with Calcofluor white die which binds to cellulose/chitin
-  Lesions fluoresce yellow-green in Wood’s light
-  See mixture of pseudohyphae and clusters of yeast
Culture
-  Grows in Sabouraud agar only if containing lipid / -  Causes discolored skin without inflammation
-  Overgrowth of yeast in lesions
Complications
ð  Premature infants who are given intralipid nutrition by infected Broviac catheters.
Get generalized infection with septicemia, pneumonia
ð  AIDS patients get severe folliculitis and seborrheic dermatitis, C5a produces inflammation / -  Lipophillic yeast. Will not grow in absence of lipid
-  Normal flora of skin, especially oily skin
-  Grows ONLY in stratum corneum
-  Not a severe disease / -  Keratinolytic (propylene glycol)
-  Selenium sulfide
(dandruff shampoo)
-  Azole
Used for severe recurrent infections of unknown etiology
Dermatophytosis (Ringworm) – Keratinized tissues
1.  Trichophyton – micro/macro conidium
2.  Microsporum – micro/macro conidium
3.  Epidermophyton – Thallic - soliatary
-  Distinguished by details of spores produced in vitro. Spores not produced in vivo. Telomorphs are possible, too.
Labs/Microscopy
-  KOH mount – removes everything except chitin in cell walls
See branching hyphae with septa +- arthrospores
-  Sabouraud culture at 30°C 2-4 weeks is ESSENTIAL since many species
-  Use cyclohexamide + antibacterial in culture / -  Outside: Ring of inflammation
-  Middle: mycelium
-  Can scratch and re-inoculate the middle
Arthrospores
Branching, septate hyphe / -  True pathogens. Not normal flora.
-  Anthropophilic species usually not as severe as zoophilic or geophilic
Virulence factors
-  Proteinases
Keratinase, elastase, collagenase
-  Sulfite
Reduces disulfide bonds in keratin / -  Perhaps nitrite as treatment since nitrosylated keratin is toxic to fungi
Tinea pedis (Athlete’s Foot) / -  Trichophyton rubum
-  Trichophyton mentagrophytes
variant interdigitale / -  Most often between 4th and 5th toe
-  Can be symptom-free carrier
-  Picked up from infected skin scales containing arthrospores / -  Anthropophillic
Tinea cruris
(Jock itch) / -  Trichophyton rubum
-  Epidermophyton floccosum
KOH mount: see branching hyphae with septa
Tinea corporis / Caused by several species that are
-  Zoophilic (ex. Microsporium canis)
-  Geophilic – requires high dose/immunocomp.
-  Anthropophilic – less common, less inflamm. / -  Ringworm on body, arms, trunk
-  Incubation period is up to 3 weeks
-  Especially susceptible with skin abrasion and perpetual dampness (Vietnam) / -  Poor invasiveness since no growth at 37C and unable to access Fe in deep tissues
-  T-cell mediated immunity is important (AIDS get severe)
-  Natural antifungal skin fatty acid / - 
Dermatophytosis (Ringworm) – Keratinized tissues (Continued) / ©2009 Mark Tuttle
Name / Diagnosis/Labs / Symptoms/ Pathogenesis / Treatment
Tinea capitis / Ectothrix: Grows within/outside hair
-  Microsporum cani/audouinii
-  Most common before puberty
Endothrix: Grows within hair only
-  Trichophyton tonsurans (monk)
-  Continues after puberty
Labs
-  Fluoresce in Wood’s Light / -  Hair becomes infected and breaks off leaving patches of baldness
Favus – comes out the end of the hair follicle
-  Scarring disease of hair follicle. T. schoenleinii
Kerion
-  Boggy tumor associated with inflammatory response to infected hair follicles
Id reactions
-  Inflammation and blistering at distal sites where no infection is present / Limited areas: Topical agents
-  Tinactin, clotrimazole
-  Whitfield ointment
(Benzoic + salicylic acids)
Large areas: Oral therapy
-  Azoles, Griseofulvin, allylamines
Epidemics
-  X-irradiation, griseofulvin, azole antifungal
Onychomycosis / Nail infection, often due to dermatophytes. Hardest to treat and may be mixed with bacteria
Mycotic Keratitis / Fungal infection of the eye.