skin 8: fungi Flashcards
Malassezia furfur causes ??
Pityriasis versicolor (aka tinea versicolor aka Pityrosporum obiculare) A chronic, mild, generally asymptomatic infection of the *stratum corneum* (cornified layers of the epidermis).
Malassezia furfur: NF?
ubiquitous saprophyte is considered normal flora when present in the yeast phase alone.
It is lipophilic and lipid dependent. *ubiquitous
It is not known what causes the transition to the hyphal phase: responsible for disease
Malassezia furfur: is it common?? where does it occur? seasonality?
Very common. Tropical areas can have a prevalence as high as 40% and the frequency is higher during summer months in temperate climates. (when wearing less clothes, skin looks like not tanning evenly)
Malassezia furfur: transmission/reservoir
only found on humans. It can be part of the normal flora.
Malassezia furfur: age?
Young adults are most frequently affected.
There is no sex or race predilection.
known EXogenous risk factors for Malassezia furfur
ENdogenous risk factors??
high temperatures, high relative
humidity
application of oily preparations, creams, greasy skin malnutrition; steroid usage; hyperhidrosis; abx tx; DM; immunosuppression, and slow rate of epithelial cell turnover (vitamin A deficiency?)
Malassezia furfur clinical manifestations: Pityriasis versicolor (synonym: tinea versicolor).
commonly involves: upper trunk, scalp, face and flexural areas
lesions are reddish-brown or, more often, *hypopigmented, sometimes with a very fine scale.
-substance produced by the organism that inhibits melanosome production and transfer of melanin. (ddx vitiligo)
In *hyperpigmented areas, production of larger, unpackaged and heavily melanized melanosomes has been demonstrated.
Erythema is absent and there is no pruritus.
additional manifestations of Malassezia furfur:
Pityrosporum folliculitis Seborrheic dermatitis Dandruff (especially pruritic dandruff. Itchy flakey scalp) Atopic dermatitis Septicemia/pneumonia
M. furfur
Pityrosporum folliculitis
(Often associated with pityriasis versicolor in the
same patient)
The organism initiates a hyperkeratosis that plugs the follicle and leads to rupture and produces granulomatous inflammation.
The result is minute, perifollicular papules and pustules, usually on the upper trunk and upper arms. These may resemble acne
M. furfur
Seborrheic dermatitis
red scaly lesions predominantly located on the scalp, face and upper trunk. Some individuals are immune hyper-responders and even the normal number of Malassezia will start an inflammatory reaction.
M. furfur
Atopic dermatitis
Atopic dermatitis (AD) is a chronic pruritic dermatitis that has unknown etiology. There is a growing association between M. furfur and other Malassezia sp. and induction of atopic dermatitis in adults seems to be related to induction beta-defensins in the skin.
(dandruff)
use shampoo that contains selenium sulfide or ASA
M. furfur Septicemia/pneumonia
Increasingly recognized cause of septicemia and death in stem cell transplant patients.
M. furfur Seborrheic dermatitis tx
Antifungals vs. steroids are now recommended as primary treatment. Data suggest that once-daily ketoconazole gel 2% is an effective treatment for seborrheic dermatitis and a viable alternative to the ketoconazole cream 2% formulation.
Toll-like receptor 2 modifiers (decreases the topical IL-8 expression) are also showing promise in decreasing the M. furfur- associated seborrheic dermatitis relapse rate
(if think acne and try abx–>ineffective)
(if tx with corticosteroids: may go away then come back)
M. furfur dx
Topical lesions exhibit pale fluoresce with Wood’s lamp.
KOH preparation of skin scrapings reveal clusters of yeast and irregular hyphae (spaghetti and meatball appearance in cases acquired in N. America).
M. furfur px and tx
For pityriasis a 1-2.5% selenium sulfide ointment or shampoo, topical keratinolytic agents or polyene glycol is used.
For seborrheic dermatitis and dandruff, ciclopirox plus salicylic acid group is recommended.
Relapses are frequent. (never completely cured, but controlled)
For hyperpigmentation topical cycloserine has been shown to be very effective.
Tinea nigra synonyms
(Keratomycosis nigra)
Hortaea (Exophiala) werneckii
Tinea Nigra Palmaris, Keratomycosis Nigricans Palmaris, Pityriasis Nigra
Tinea nigra etiologic agent
Hortaea (formally Exophiala) werneckii.
Tinea nigra found where geographically??
Central and S. America, Cuba, Puerto Rico, S.E. Asia, Indonesia, Florida and other coastal states of S.E. U.S.A.
T. nigra acquired how?
incubation period?
Direct inoculation onto the skin from contact with decaying vegetation, wood or soil
Incubation periods may be as long as 20 years In the U.S.
T. nigra age/gender/seasonality
95% of infections occur under the age of 18 yr. and 75% of those affected are female (in the US, ww varies)
-typically present w. cosmetic problem they want taken care of
no seasonality
T. nigra risk factors
Contact with plant material and through auto-inoculation. Predisposing
factors are not understood.
T. nigra s/s
A discrete, 1-8 cm dark, brown-to-black, mottled, macule forms most often on the palm or palmar surface of the fingers, although the soles may also be involved. There is no inflammation, induration or scaling.
Lesions are asymptomatic.
T. nigra dx
KOH prep of skin scraping
Tinea nigra must be differentiated from ??
malignant melanoma and
junctional nevus.
T. nigra tx
topical agents
Black and White Piedra agents
black: Piedra hortai
white: Trichosporon beigelii
Black and White Piedra are ectothrix infections which can involve ??
any hair on the body, but are most often seen on the face, head, and genital areas. T
ectothrix??
a sheath of arthrospores is produced on the external surface only of the hair shaft
(spore on outside of hair shaft)
makes hair look “ratty”
Black and White Piedra found where ??
worldwide.
White piedra is emerging as a commonly seen hair and scalp infection in the northeastern United States.
Neither black nor white piedra involve the ??
symptoms??
follicular portion of the hair or the epidermis
usually no symptoms
White piedra looks like a white nodule (little white flecks) on the hair shaft and must be distinguished from ??
nits and lice.
Black piedra forms a brown/black collar around the hair shaft. Resembles the ectothrix caused by ?? but is not ??
Microsporum
fluorescent.
Black and White Piedra tx
Cut or shave off the affected hair is still the best treatment
recent studies indicate that scalp and hair infection may be successfully treated with a combination of oral azole antifungals and shampoos without shaving the scalp.
