Mycology lec 3 & 4

Cutaneous Mycosis

Dr., Huda Ibrahim

DermatophytesFrequency of species

Tinea capitis
2 major clinical types : 1- Inflammatory types include A- Kerion , is scaly , erythematous lesion with bogginess & excuding pus caused by M.canis mainly. B-Favua , is a concave yellow crusts called scutula , can lead to permanent alopecia. Caused by T.schoenlenii

2- Non-inflammatory

A- Gray patch , multiple scaly lesion with stubs of broken hair. Caused by M.audouinii.B –Black dot , multiple area of alopecia studded with black dots. T.tonsurans is the usual causative agents

Black dot ringworm caused by Trichophyton tonsurans

Kerion: inflammatory of tinea capitis caused by Microsporum canis or Trichophyton mentagrophytes



Favus of scalp showing scutulae

Types of hair invaders

. Ectothrix invasion is characterised by the development of arthroconidia on the outside of the hair shaft. The cuticle of the hair is destroyed and infected hairs usually fluoresce a bright greenish yellow colour under Wood's ultraviolet light. Common agents include M. canis, M. gypseum, T. mentagrophyte and T. verrucosum


Endothrix hair invasion is characterised by the development of arthroconidia within the hair shaft do not fluoresce. The cuticle of the hair remains. All endothrix producing agents are anthropophilic e.g T. tonsurans and T. violaceum.

Ectothrix and Endothrix

Fluorescing hair (under Wood's lamp) is seen in dogs and cats infected with some dermatophytes

KOH examination

Is a very useful test for the laboratory diagnosis of fungal infection of tissues especially skin, hair and nails. KOH separates the fungal elements from intact cells as it digests the protein debris and dissolves cement substances that holds the keratinized cells together and makes it easy to visualize under the microscope.

Culture

Final and exact identification of causative fungusSeveral infected hairs are placed on Sabouraud’s glucose agar(4 weeks) or Dermatophyte Test Medium (DTM)-for 2-4 weeks

Treatment

Griseofulvin 500mg for 2-4 months, or for at least 2 weeks after a negative microscopic and culture examinations are obtained. Terbinafine tab.250mg systemic steroids, to minimize scarring, can be given simultaneously Selenium sulfide shampoo or ketaconazole shampoo three times weekly can be used as adjunctive therapy to oral antifungal agents.


Tinea Corporis(Tinea Circinata)
Sites of prediliction are neck, upper and lower extremities, and trunk Can be caused by any dermatophyte.T. rubrum is is the most common dermatophyte . Characterized by one or more circular, sharply circumcsribed. Lesions may be slightly elevated, particularly at the border, where they are more inflamed and scaly than at the central part

Tinea corporis: note sharp margin and central clearing

Tinea Cruris
jock itch Most common in men , on upper inner thigh Begins as a small erythematous and scaling or vesicular and crusted patch Spreads peripherally and partly clears in the center Characterized by its curved, well-defined border, especially at lower edge May extend downward on thighs and backward on the perineum or anus .Keep dry as possible. T. mentagrophytes & E. floccosum & T. rubrum are usual cause

Tinea cruris in a woman

Tinea pedis
Popularly called athlete’s footMost common fungal disease Most commonly the third toe web is involvedSweat on soles and in between has a high pH, is a good culture medium for the fungus. Trichophyton mentagrophytes produces an acutely inflammatory condition. Trichophyton rubrum produces non-inflammatory condition(a moccasin or sandel appearance)

Tinea pedis showing interdigital scalping T. mentagrophytes

Dermatophytosof the soles Trichophyton mantagrophytes

Trichophyton rubrum

T. rubrum causes the majority of cases Produces a relatively non-inflammatory type of dermatophytosis characterized by a dull erythema and prnounced scaling involving the entire sole and sides of feet Producing a moccasin or sandel appearance

Prophylaxis

Dry toes after bathing Dryness is essential if re-infection is to be avoided Use good antiseptic powder on feet after bathing-particularly between toes e.g., Tolnaftate powder. Plain talc, may be dusted into socks and shoes to keep feet dry. Topical Azole &keratolytic agent included in Rx.

Onychomycosis(Tinea Ungium)

Fungal infection of nail Represents up to 30% of diagnosed superficial fungal infections Etiologic agents are species: Epidermophyton,, and Trichophyton fungi Nail plate become friable, yellow, or white as in trichophyton infections May also be caused by C. albicans and here nail plate remains hard .

Candidiasis

Candida proliferates in outer layers of the stratum corneum where horny cells are desquamating It does not attack hair, It is largely an opportunisitic organism, able to behave as a pathogen mainly in impaired immune status, or in body folds Moisture promotes its growth, in moist lip corners

Diagnosis

Demonstration of the pathogenic yeast C. albicans establishes the diagnosisUnder microscope KOH prep may show spores and pseudomyceliumOn gram stain yeast forms are dense, gram-positive, ovoid bodies, 2-5 um in diameterIn culture Culture on Sabouraud’s glucose agar shows a growth of creamy, grayish, moist colonies in about 4 days .Azole & Terbinafine can be included in treatment.

Oral Candidiasis (BabiesThrush)

Mucous membrane of the mouth may be involved in healthy newborn & marasmic infant Newborn infection may be acquired from contact with vaginal tract of mother. Grayish white membranous plaques are found on surface. Base of plaques are moist, reddish, and macerated. It can occur in adult in immunocompromised pt. Papillae of tongue are atrophied, surface is smooth, glazed, and bright red.

Candidal Vulvovaginitis

C. albicans is a common inhabitant of vaginal tract May cause severe pruritus, irritation, and extreme burning Labia may be erythemtous, moist, and macerated and cervix hyperemic, swollen, and eroded, showing small vesicles on its surface Vaginal discharge is not usually profuse but is frequently thick and tenacious

Risk factors

Due to disruption of normal microbiota May develop during in pregnancy, in diabetes, or secondary to therapy with a broad- spectrum antibiotic , I.U.C.D Recurrent vulvovaginal candidiasis has been associated with long-term tamoxifen, oral contraceptive pills.

Candidal Intertrigo

Pruritic intertriginous eruptions caused by C. albicans may arise between folds of genitals; in groins or armpits; between buttocks; under large pendulous breasts; under overhanging abdominal folds; or in umbilicusPinkish intertriginous moist patches are surrounded by a thin macerated epidermis (“collarette” scale)

Pseudo Diaper Rash

In infants, C. albicans infection may start in perianal region and spread over entire areaDermatits is enhanced by maceration produced by wet diapersScaly macules and vesicles with maceration in involved areas cause burning, pruritis . Diagnosis may be suspected by finding involvement of folds and occurrence of many small erythematous desquamating “satellite” or “daughter” lesions scattered around edges.Perianal candidiasis can occur & can involve entire G.I.T

Candidal Paronychia

Chronic inflammation of nail fold produces occasional discharge of thin pus, gradual thickening and brownish discoloration of nail plates, and development of pronounced transverse ridges Mostly finger nails are affected frequently occur in person whose hands in water or who handle moist objects

Onychomycosis caused by Candida albicans in mucocutaneous candidiasis

Intertrdigital candidal infection
Usually white, thick and does not peel off freely On feet fourth interspace is most often involved Areas are apt to be multiple Clinically indistinguishable from tinea pedis Dx made by culture Tx is with topical anticandidal preparations

Candida fingerweb erosion：related to fatness , occupation etc.

THE END
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