Considered as cosmetic infections where no pathologic changes are observed or living tissue is invaded or cellular host response to the fungi (Non-irritating/ asymptomatic infection)
Superficial mycoses
Two varieties of superficial mycoses
→ White: Pityriasis Versicolor, White Piedra
→ Black: Tinea Nigra, Black Piedra
*piedra: hair
Organism which causes tinea nigra
Exophiala werneckii
Organism which causes WHITE piedra
Trichosporon beigelii
Organism which causes black piedra
Piedraia hortae
Also known as Pityriasis versicolor and “An-an”
Tinea versicolor
species under genus Malasezzia which is not lipophilic
M. pachydermatis
most common isolates under genus Malasezzia
M globosa and restricta
other diseases caused by Genus Malassezia
dandruff (restricta)
Seborrheic dermatitis (restricta and sympodialis)
folliculitis
septicemia
clinical features of tinea versicolor
FLAT macular and demarcated lesions (with thin chalky branny scales)
T or F: Pigmentation of tinea versicolor lesions depend on patient’s skin color
true
What makes oily body parts (FANTS) or sebum harbor tinea versicolor pathogens?
waxy esters, fatty acids, triglycerides
Tinea versicolor should be differentially diagnosed from
tinea alba (does not affect extremities usually) vitiligo
color of tinea versicolor lesions under woodlamp
pale green
specimen used for microscopic examination of tinea versicolor
skin scrapings
smear used for diagnosing skin scrapings of tinea versicolor
KOH with Parker ink
*only edges of the fungi are seen with KOH only
direct microscopic examination of tinea versicolor under KOH and PAS shows
spaghetti (blastospores) and meatballs (angular hyphal elements) appearance
*pathognomonic
media used for culturing tinea versicolor
PDA with fatty acids
*circular convex creamy colonies
it is a slow-growing saprophytic dematiaceous fungi found in soil, compost, humus and wood
exophiala werneckii
tinea nigra is most commonly found where
palms
clinical manifestation of tinea nigra
non-scaling and non-inflammatory well-demarcated gray to brown-black macular lesions
tinea nigra must be differentially diagnosed from
chemical burns
skin cell carcinoma
seen under light microscope for tinea nigra
Pigmented brown to dark olivaceous septate hyphal elements
Budding 2-cell yeast with melanized cell walls
darkly pigmented septa between 2 cells part of the outer cell wall in tinea nigra
annelide
aged tinea nigra on PDA is characterized by
abundant aerial mycelia and velvety, dark olive in color
tinea nigra in LPCB
2- celled (cylindrical and spindle-shaped) pale brown yeast cells
piedra meaning
small stone
*due to firm irregular nodules
the mass of fungus in piedra can be found in
hair shaft
clinical features of black piedra
Discrete, hard, more compact, gritty, brown to black concretions
or nodules
commonness of black piedra
Scalp hair > Beard, mustache > Axilla and groin hairs – rare
specimen collected for black piedra
hair with nodules
*with 25% KOH or NaOH
seen under direct microscopic examination for black piedra
→ Dark septate hyphae
→ Round to oval asci
→ Hyaline, curved to fusiform ascospore, a sexual spore
media used to isolate black piedra
SDA with chloramphenicol
SDA with cycloheximide
*very slow growth and island colonies
black piedra in isolated culture is characterized by
→ Dark brown to black colonies with greenish brown, short aerial mycelium
etiologic agent of white piedra
Trichosporon beigelii or Trichosporon cutaneum
t or F: white piedra commonly appears in scalp, eyebrows and lashes
false: face, axilla, genitals
specimen used for diagnosis
hair with nodules (+ 10% KOH or 25%NaOH + 5% glycerin)
isolation of white piedra (same as black but without cycloheximide)
SDA with chloramphenicol without cycloheximide (rapid)
LPCB (Hyaline hyphae, Arthroconidia, Blastoconidia)
other characteristics of WHITE PIEDRA
→ Non-carbohydrate fermenting → Assimilates dextrose, lactose, D-xylose and inositol → Negative KNO3 assimilation → Urease positive → Splits arbutin