Dermatomycoses: superficial infections Flashcards
How are dermatophytes transmitted?
Direct contact with spores, or infested hair or skin scales
Pathogenesis of dermatomycoses
Spores adhere to keratinized tissue (epidermis) –> germinate –> secrete keratinases –> invade/grow
WITHOUT eliciting host immune response (nondestructive/asymptomatic)
Four kinds of superficial dermatomycosis infections:
Hair of the scalp: 1) black piedra 2) white piedra Hairless skin: 3) tinea/pityriasis versicolor 4) tinea/pityriasis nigra *Tinea = infection of hairless skin*
What is the cause of pityriasis versicolor?
The yeast, malassezia furfur.
The yeast is lipophilic and grows best in warm temperatures/humidity.
Where in/on the skin does the infection of malassezia furfur take place?
Stratum corneum
Clinical presentation of pityriasis versicolor?
Look up some pics! (I thought these were just sun spots..)
Brownish red and de-pigmented lesions, scaly patches of skin
Usually affect the trunk most
No inflammation/no itch.
Relapse is frequent.
How do we diagnoses pityriasis versicolor?
Yellow-green fluorescence (in keeping with the italian theme of sketchy, I like to think pesto-ish) on examination by Wood’s lamp …
oOoOh ambiance.
Treatment for pityriasis versicolor
Topical: selenium sulfide shampoo, other options for shampoos and lotions, topical terbinafine, and/or benzoyl peroxide
For shampoos- leave in for 10 minutes then wash out, repeat for 7 days, then once a month for 6 months.
If patient isn’t responding to primary pit. versi. treatment…
go with systemic therapy (ketoco-, fluco-, or itraconazole)
What is the cause of pityriasis nigra? Where does it infect?
- Exophiala werneckii
- Stratum Corneum again
Clinical presentation of tinea nigra
Pictures pictures!
most are asymptomatic but…
-Brown to black NONSCALY macules with well-defined borders
-Palm surfaces are most affected
Where are tinea nigra infections most common?
Tropical climates and frequent contact with decaying vegetation, wood, soil
Diagnose tinea nigra, please.
Treat a superficial scraping with KOH
Look for abundant branched septate/fragmented hyphae
Treatment for tinea nigra
Oral azoles
Cutaneous dermatomycoses are also known as:
Ringworm: infection of superficial keratinized tissues, hair, skin, and nails
… slightly deeper in the epidermis than superficial mycosis
What is the ONLY contagious fungal infection?
Dermatophytosis
Three genera of dermatophytes (species in parentheses)
Microsporum (audouinii)
Epidermophyton (floccosum)
Trichophyton (rubrum, tonsurans, mentagrophytes, schoenleinii)
Dermatophytes are classified according to mode of transmission. What are the three kinds?
1) Geophilic-from soil
2) Zoophilic- from animals
Both of these produce acute inflammatory infections in humans; easily treated
3) Anthropophilc- from humans
Produce mild to chronic infxn; difficult to eradicate
3 diagnostic clues for dermatophytes
1) presence of septate
2) branching hyphae
3) chains of arthroconidia
Identifiying microsporum
Ectothrix- dense sheath of spores around hair
Identifying trichophyton
Endothrix- produce arthroconidia inside hair shaft
Identifying epidermophyton
BANANA BUNCHES (thin-walled macroconidia)
Name the body part that goes with the type of tinea!
Capitis, Pedis, Barbae, Corporis, Ungulum, Manus, Cruris
- Head
- Feet
- Beard
- Body
- Nail
- Fingers/palm
- Crotch (jock itch)
Most common cause of tinea capitis?
Trichophyton tonsurans
Scaly lesions on scalp, eyebrows, eyelashes
Epidemiology and at risk people for tinea capitis
- Children 4-14 y.o.
- Classmates
- Family members
- Overcrowded areas, poor hygiene, and protein mulnurished
Treatment for Tinea capitis
Griseofulvin and Ketoconazole
2 infectious agents for Tinea barbae
- T. mentagrophytes (a beard is “meant ta grow” wink wink)
- T. verrucosum
Who is most commonly affected by Tinea barbae?
Adult men in frequent contact with cattle, dogs, other animals (dairy farmers and cattle ranchers)
Barbershop guys
Clinical presentation of Tinea barbae
Endothrix- diffuse erythema and perifollicular papules and pustules
-Inflammatory type is usually unilateral and spares the upper lip; nodular lesions covered with cursts; hair becomes brittle
Treatment for Tinea barbae?
Systemic antifungal agents.
Causes of Tinea corporis and Tinea faciei?
- Trichophyton rubrum
- Microsporum canis
Clinical presentation of Tinea corporis and Tinea faciei?
Active erythematous ring with spreading borders with a cleared center on hairless regions of skin and face
Inflammatory and Non-inflammatory lesions
Treatment for inflammatory Tinea corporis and Tinea faciei?
Systemic therapy progression: Ketoconazole, itraconazole, terbinafine, griseofulvin
Just a reminder: as the name implies, M. canis can be transmitted by direct contact with infected animals, humans, or contaminated clothing
:)
The sciencey name for athlete’s foot is…
Tinea pedis = ringworm of the foot especially in between toes
Frequent causes of Tinea pedis?
- Epidermophyton floccosum
- Trichophyton rubrum
Clinical presentation of Tinea pedis?
Vesicular or ulcerative… super itchy. kinda looks like dead skin
Epidemiology of Tinea pedis?
Common in athletes, related to footwear, common showers, and pool floors.
Treatment of Tinea pedis?
Systemic therapy progression: Ketoconazole, itraconazole, terbinafine, griseofulvin
This is getting boring…let’s talk about Jock itch. (where and cause)
aka Tinea Cruris = ringworm of the groin, perineum and perianal region
Mostly caused by E. Floccosum
What does jock itch look like?
Sharp demarcated lesions with raised erythematous margin, lesions in genitocrural area and medial upper thigh, scrotum hardly affected.
Can you get jock itch from indirect contact with contaminated objects?
Yes so try not to share gym towels, or gym equipment. Trust no one at the gym.
Treatment for Tinea cruris?
Topical treatments
Treatment for non-inflammatory Tinea Corporis?
Topical treatments
Cause and treatment for Tinea manus?
T. rubrum
Treat with topicals
What is onychomycosis?
Infection of the nail plate seen in tinea ungulum
Three common causes of Tinea ungulum?
T. rubrum (as in corporis, faciei, and manus)
T.mentagrophytes (as in barbae)
E. floccosum (as in pedis and cruris)
Who is at risk of developing Tinea ungulum?
Elderly with reduced peripheral circulation, diabetics, those with increased nail trauma
Chronic water exposure
Poor hygiene
Immunodeficient
Treatment for Tinea ungulum?
Systemic antifungals.
Name the only subcutaneous mycosis that we talked about and its cause.
Sporotrichosis caused by sporothrix schenckii.
Who is most at risk for developing sporotrichosis?
People who work with soil and vegetation (i.e. flower shop employees)
Sporothrix Schenckii is dimorphic meaning…
Mold in the cold, yeast in the heat.
Room temp: branching septate hyphae with microcondia
In the body: elongated yeasts
What are two buzz word plants for sporotrichosis?
Sphagnum moss and roses
Pathogenesis of sporotrichosis
NOT spread person to person.
-Enter through thorn prick or splinter (needs an opening)
OR
-Rarely, inhaling conidia –> pulmonary infection
How long does it take for sporotrichosis symptoms to appear after exposure?
1-12 weeks
What are the four categories of sporotrichosis?
1) Lymphocutaneous (most common)
2) Pulmonary (rare)
3) Osteoarticular -direct inoculation or haematogenous seeding in bones
4) Disseminated (rare)- cutaneous lesions and multiple visceral organ involvement; most common in AIDS pts.
Describe the progression of lymphocutaneous sporotrichosis
= inflamed pusy subcutaneous nodules progressing proximally along lymph channels
Small painless bump resembling insect bite –> one or more additional boil-like nodules spread along lymph –> eventually lesions look like open sores
Very slow to heal
Treatment for sporotrichosis:
Prolonged therapy of itraconazole or fluconazole for cutaneous lesions.
Amph B for relapses and serious infections
