24 - 160 - SUPERFICIAL FUNGAL INFECTION Flashcards
most common cause of dermatophytosis of the skin
Trichophyton rubrum
most common cause of tinea capitis
Trichophyton tonsurans
Knobby antler-like hyphae (favic chandeliers), numerous chlamydoconidia.
Trichophyton schoenleinii
Most specific test for onychomycosis
Culture
Most sensitive test for onychomycosis
PAS examination of nail clippings
Which dermatophytes will produce fluorescence on wood lamp
(+) fluorescence in wood lamp
True/ false. T. Tonsurans which is the most common cause of tinea capitis will not fluoresce on wood lamp.
Enumerate dermatophytes with (+) fluorescence:
TRUE
Enumerate dermatophytes with (+) fluorescence:
Microsporum canis, audouinii, distortum, ferrugineum - yellow-green
T. Schoenleinii - blue-gray (favus)
Dermatophytosis of the hair
piedra
acute inflammatory dermatitis at sites distant from the primary inflammatory fungal infection
dermatophytid or id reaction (autoeczematization)
KOH finding of dermatophytes
Long, narrow, septated and branching hyphae
culture medium for dermatophytes
*** Sabouraud medium **(4% peptone, 1% glucose, agar, water).
* Modified Sabouraud medium (addition of chloramphenicol, cycloheximide, and gentamicin).
positive reaction in Dermatophyte test medium
ncubation at room temperature for 5 to 14 days results in change in medium color from yellow to bright red in the presence of a dermatophyte.
stains to visualize dermatophytes in histopathology
- Periodic acid-Schiff (PAS) - pink
- Grocott Methenamine Silver (GMS) - black
% of false-negative results in KOH
15%
% og KOH used for dermatophyte identification
10% to 20% KOH preparation
how can you aid penetration of KOH into keratin
- Penetration of KOH into keratin may be aided by either slightly warming the slide with a low-intensity flame or by addition of dimethylsulfoxide (DMSO) in KOH solution
- Some may also find the adding a drop of blue or black stain such as chlorazol black (in similar fashion as KOH solution above) helpful for better identifying fungal elements
most commonly used isolation medium for dermatophytes and it serves as the medium on which most morphologic descriptions are based.
Sabouraud dextrose agar (SDA)
Elimination of contaminant molds, yeast, and bacteria is achieved by the addition of **cycloheximide and chloramphenicol (± gentamicin) **to the medium making it highly selective for the isolation of dermatophytes.
this general has smooth walled microconidia
Trichophyton
this general has rough-walled MACROconidia
Microsporum
this general has smooth-walled MACROconidia
Epidermophyton
test to differentiate T. interdigitale and rubrum
Differentiates Microsporum species
most sensitive test for onychomycosis
PAS examination of nail clippings - most sensitive
Culture - most specific
Whereas culture is the most specific test for onychomycosis, PAS examination of nail clippings is the most sensitive and obviates the need to wait weeks for a result
MC cause of Distolateral subungual onychomycosis
Trichophyton rubrum, Trichophyton interdigitale
MC cause of Proximal subungual onychomycosis
Trichophyton rubrum, Trichophyton megninii
MC cause of White superficial onychomycosis
Trichophyton interdigitale
MC cause of Total dystrophic onychomycosis
Candida sp.
MC of black dot tinea capitis
Trichophyton tonsurans, Trichophyton violaceum
MC cause of favus
Trichophyton schoenleinii, Trichophyton violaceum, Trichophyton mentagrophytes
MC cause of Tinea corporis in adults and children
Adults: Trichophyton rubrum
Children: Microsporum canis
MC cause of tinea incognito
Trichophyton rubrum
MC cause of Tinea imbricata
Trichophyton concentricum
MC cause of tinea cruris
- Trichophyton rubrum,
- Epidermophyton floccosum,
- Trichophyton interdigitale,
- Trichophyton verrucosum
MC cause of Tinea nigra
Hortaea werneckii
MC cause of interdigital tinea pedis
- Trichophyton rubrum,
- Trichophyton interdigitale,
- Epidermophyton floccosum
MC cause of tinea manuum
- Trichophyton rubrum,
- Trichophyton interdigitale,
- Epidermophyton floccosum
course and prognosis of dermatophyte infection
- The clinical course of dermatophytosis varies according to** pathogen and host factors**.
- some dermatophytes are able to** evade or suppress host immune function,** and
- some hosts are unable to mount an effective immune response to clear infection.
- As such, the severity of each infection is variable according to the combination of these factors.
Pregnancy category of fluconazole
D
Pregnancy category of griseofulvin
X
Pregnancy category of itraconazole
C
Pregnancy category of terbinafine
B
describes fungal infection of the nail caused by dermatophytes, nondermatophyte molds, or yeasts
Onychomycosis
refers strictly to dermatophyte infection of the nail
Tinea unguium
3 types of onychomycosis
(a) distolateral subungual onychomycosis (DLSO),
(b) proximal subungual onychomycosis (PSO), and
(c) white superficial onychomycosis (WSO)
most common form of onychomycosis
distolateral subungual onychomycosis (DLSO)
It begins with invasion of the stratum corneum of the hyponychium and distal nail bed, forming a whitish to brownish–yellow opacification at the distal edge of the nail
patients with this type of onychomycosis should be screened for HIV, as it has been identified as an a marker for this disease
proximal subungual onychomycosis (PSO)
these subspecies are responsible for approximately 90% of all cases of onychomycosis
T. rubrum and T. interdigitale
in this type of onychomycosis, on histology, the organisms are present superficially on the dorsal nail and display unique “perforating organs” and “eroding fronds.”
White Superficial Onychomycosis
An oral antifungal is required for onychomycosis involving what part of the nail?
nail matrix
or when a shorter treatment regimen or higher chance for clearance/cure is desired
This drug is no longer considered standard treatment for onychomycosis because of its prolonged treatment course, potential for adverse effects and drug interactions, and its relatively low cure rates
griseofulvin
Black piedra is caused by
Piedraia hortae
white piedra is caused by pathogenic species of what genus?
Trichosporon genus, namely Trichosporon asahii, Trichosporon ovoides, Trichosporon inkin, Trichosporon mucoides, Trichosporon asteroides, and Trichosporon cutaneum
NOT TRICHOPHYTON
area most commonly affected in black piedra
scalp hair
area most commonly affected in white piedra
facial, axillary, and genital hair more commonly than scalp hair
T. ovoides is found more commonly on scalp hair, T. inkin on pubic hair, and T. asahii on other body surfaces.
2 forms of tinea barbae
superficial
inflammatory
most common clinical presentation of tinea barbae
inflammatory type
It presents analogously to kerion formation in tinea capitis with boggy-crusted plaques and a seropurulent discharge
MC causes of tinea barbae
Tinea barbae is most commonly caused by the zoophilic strains of T. interdigitale (formerly named Trichophyton mentagrophytes var. mentagrophytes), **T. verrucosum, **and, less commonly, M. canis
forms of tinea capitis
- Noninflammatory type
- “Black Dot” Tinea Capitis
- Inflammatory Type
MC causes of noninflammatory tinea capitis
M. audouinii or Microsporum ferrugineum
Alopecia may be imperceptible or, in more inflammatory cases, may have circumscribed erythematous scaly patches of nonscarring alopecia with breakage of hairs.
What type of tinea capitis is this?
Where does it frequently occur?
“gray patch” type
occiput
- under noninlammatory type
The “black dot” form of tinea capitis is typically caused by what anthropophilic endothrix organisms?
T. tonsurans and T. violaceum
Hairs broken off at the level of the scalp leave behind grouped black dots within patches of polygonal-shaped alopecia with finger-like margins.
“Black Dot” Tinea Capitis
presentation of tinea capitis that presents as a boggy, inflammatory mass studded with broken hairs and follicular orifices oozing with pus
kerion
Zoophilic or geophilic pathogens, such as M. canis, M. gypseum, and T. verrucosum, are more likely to cause this type of tinea capitis
Inflammatory Type
- Resultant inflammation ranges from follicular pustules to furunculosis or kerion.
- Intense inflammation may also result in scarring alopecia.
- The scalp is usually pruritic or tender.
- Posterior cervical lymphadenopathy is often present, and may serve as a clinical pearl in differentiating tinea capitis from other inflammatory disorders involving the scalp
this finding may serve as a clinical pearl in differentiating tinea capitis from other inflammatory disorders involving the scalp
Posterior cervical lymphadenopathy
characterized by longitudinally arranged hyphae and air spaces within the hair shaft
Favus
shampoo preparations that help eradicate dermatophytes from the scalp
- Selenium sulfide (1% and 2.5%),
- zinc pyrithione (1% and 2%),
- povidone-iodine (2.5%),
- ketoconazole (2%)
Adjunctive use of these shampoos is recommended 2 to 4 times weekly for 2 to 4 weeks
This medication may reduce the incidence of scarring associated with markedly inflammatory varieties of tinea capitis
Oral glucocorticoids
The usual regimen is prednisone 1 to 2 mg/kg each morning during the first week of therapy.
“Tinea corporis gladiatorum” is caused most commonly by
T. tonsurans
refers to any dermatophytosis of **glabrous skin **except palms, soles, and the groin.
Tinea corporis
superficial and subcutaneous dermatophytic infection involving deeper portions of the hair follicles, presenting as scaly, follicular papules and nodules that coalesce in an annular arrangement
Majocchi granuloma
- most commonly caused by T. rubrum, T. interdigitale, and M. canis.
- observed on the legs of women who become inoculated after shaving or who apply topical corticosteroids to the involved area, thereby facilitating infection
dermatophytosis of the groin, genitalia, pubic area, and perineal and perianal skin
Tinea cruris
It is the second-most common type of dermatophytosis worldwide.
Tinea cruris
Plaques in tinea cruris caused by this dermatophyte are more likely to demonstrate central clearing with involvement of the genitocrural crease and medial upper thigh
E. floccosum
plaques in tinea cruris caused by this dermatophyte coalesce with extension to the pubic, perianal, buttock, and lower abdominal areas
T. rubrum
chronic dermatophyte infection of the scalp that rarely involves glabrous skin and/or nails, and is characterized by thick yellow crusts (scutula) within the hair follicles that lead to scarring alopecia
Tinea favosa or favus
most common cause of human favus
Trichophyton schoenleinii
exhibits subtle, blue-gray fluorescence along the entire hair with Wood lamp examination
cause of tinea nigra
Hortaea werneckii
- found on otherwise healthy people and presents typically as an asymptomatic, mottled brown to greenish-black macule or patch with minimal to no scale on the palms or soles
- The macule is often darkest at the advancing border.
- Because of its coloration and location on palms and soles, tinea nigra is frequently misdiagnosed as acral lentiginous melanoma.
Tinea nigra
KOH examination of scrapings reveals brown to olive-colored, thick branching hyphae, along with oval to spindle-shaped yeast cells that occur singly or in pairs with a central transverse septum
tinea nigra
Infection of the dorsal aspects of feet and hands is considered to be what type of dermatophytosis?
tinea corporis
most common dermatophytoses
tinea pedis and tinea manuum
type or forms of tinea pedis
- Interdigital Type
- Chronic Hyperkeratotic (Moccasin) Type
- Vesiculobullous Type
- Acute Ulcerative Type
- Vesicular Id Reaction
the most common presentation of tinea pedis
Interdigital Type
- begins as scaling, erythema, and maceration of the interdigital and subdigital skin of the feet, particularly between the lateral third and fourth and fourth and fifth toes
most common pathogen of Chronic hyperkeratotic (moccasin) type tinea pedis
T. rubrum
MC cause of Vesiculobullous type of tinea pedis
T. interdigitale
caused by zoophilic T. interdigitale in combination with Gram-negative bacterial superinfection produces vesicles, pustules, and purulent ulcers on the plantar surface
Acute ulcerative type tinea pedis
Dermatophyte infection of the hand usually has a noninflammatory presentation with diffuse dry scaling and accentuation in the creases
Tinea Manuum
Tinea pedis and tinea manuum are caused predominantly by what dermatophyte
T. rubrum
