17 - Superficial and Cutaneous Mycoses

Question 1

What is the immunity to fungi?

Answer 1

The innate immune system protects healthy individuals from fungal infections, but some dimorphic fungi can escape these defenses.

Question 2

What is the adaptive immune response to fungi?

Answer 2

Neutrophils and Th17 metdiated immune responses in the immunocompetent.

Question 3

What are the superficial mycoses?

Answer 3

Malassezia furfur, hortaea weneckii/exophiala werneckii, piedraia hortae, and trichosporon.

Question 4

What are the cutaneous mycoses? What are the subcutetaneous ones?

Answer 4

Cuteaneous: Trichophyton rubrum and T. mentagrophytes.

Subcutaneous: sporothrix schenckii

Question 5

What infection is Malessezia furfur responsible for? What is it’s morphology and epidemiology?

Answer 5

Responsible for Pityriasis (tinea) versicolor.

Lipophilic year.

Passed between humans by direct or indirect transfer of infected keratinous material.

Question 6

What are clinical syndromes associated with Malessezia furfur? How do you diagnose it?

Answer 6

Small hypopigmented or hyperpigmented macules, depending on skin color of individual. Affected areas do not tan.

Direct microscopic visualization of fungal elements in KOH prep of epidermal scales.

Question 7

What is the treatment for Malessezia furfur?

Answer 7

Localized infection treat with topical azoles or selenium sulfide shampoo.

Widespread infection treat with oral azole.

Question 8

What infection is associated with Hortaea werneckii/exophiala wernecnkii? What is the morphology?

Answer 8

Responsible for tinea nigra.

Dematiaceous (dark colored) frequently branched septate hyphae.

Question 9

What is the epidemiology of Hortaea werneckii/exophiala wernecnkii? What are the clinical syndromes? Treatment?

Answer 9

Likely contracted by inoculation into the superficial layers of the epidermis.

Appears as a solitary irregular pigmented macule, usually on palms or soles. Can resemble malignant melanoma. Infection not contagious.

Treatment with topical agents such as azoles and terbinafine.

Question 10

What infection is caused by piedraia hortae? What is the morphology? Epidemiology?

Answer 10

Responsible for black piedra.

Brown/red mold that exhibits asci/ascospores (sexual spore).

Poor hygiene.

Question 11

What are the clinical syndromes associated with piedraia hortae?

Answer 11

Presence of hard, dark nodules that surround the hair shaft.

Asci/ascospores (buzzword) present in cement-like substance that holds the hyphal mass together.

Question 12

What is the treatment for piedraia hortae?

Answer 12

Can be cured with a haircut, proper/regular hair washing s and topical antifungal agents.

Question 13

What infection is trichosporon responsible for? What is the epidemiology? What are the clinical syndromes?

Answer 13

White piedra, which is re-emerging as a systemic mycoses in immune-compromised individuals.

Poor hygiene.

Affects hair of the groin and axillae, fungus surrounds hair shaft and forms white/brown swelling around strand.

Question 14

How do you diagnose trichosporon? How is it treated?

Answer 14

Microscopic exam of hair cells.

Cyclohexamide inhibits growth so don’t use this on the plate or you won’t see any growth.

Can be cured by removal of infected hair, improved hygiene, and topical azoles.

Question 15

What bugs are dermatophytes/ dermatophytoses?

Answer 15

Approximately 41 organisms are responsible for dermatophytic infections. The ones we need to know are:

Trichophyton, epidermophyton, and microsporum.

Question 16

What are the common characteristics of dermatophytes?

Answer 16

Ability to infect superficial keratinized tissue (skin, hair, nails).

Referred to as “tineas” or ringworm.

Question 17

What are the types of “tinea” infections?

Answer 17

Tinea capitis - scalp, eyelashes, eyebrows: can be endothrix with arthroconidia inside the hair shaft or ectothrix with arthroconidia found outside the hair shaft.

Tinea pedis: foot (athletes foot)
Tinea barbae: beard 
Tinea corporis: smooth of glaborous skin 
Tinea cruris: groin
Tinea unguium, nails (onychomycosis).

Question 18

Where are dermatophytes restricted to?

Answer 18

Most restricted to nonviable skin (dead skin) since most are unable to grow at 37 degrees of in the presence of serum.

Question 19

What is the ecology of dermatophytes (ie the different types of natural locations in which they can be found)?

Answer 19

Zoophilic - animals
Geophilic: soil
Arthropophilic - humans

Question 20

What is the epidemiology of Trichophyton rubrum and T. mentagrophytes (dermatophytes)?

Answer 20

They are anthropophilic (in humans), common world-wide, and account for 80-90% of all infections.

Question 21

What clinical symptoms occur with tinea pedis caused by dermatophytes?

Answer 21

Itching vesicles and pustules, cracked skin, macerated, peeling, watery discharge.

Question 22

What clinical symptoms occur with tinea corporis and cruris caused by dermatophytes?

Answer 22

tiny red pimp with itching and subsequent peripheral spreading with an actively inflamed vesiculo-pustular margin and healing scaly center.

Question 23

What clinical symptoms occur with tinea capitis caused by dermatophytes?

Answer 23

It spreads peripherally with patches of broken hair stumps.

Question 24

What clinical symptoms occur with tinea unguium/onychomycosis caused by dermatophytes?

Answer 24

Nails will appear thickened, cracking, and have a yellowish-brown color.

Question 25

How can dermatophytes be diagnosed?

Answer 25

Direct microscopic observation. Some fluorescne a distinct color when exposed to a wood lamp.

Can be grown on dermatophyte test media: coccidioides imitis can resemble a dermatophyte of this medium and represents a serious biohazard (so be carful when looking at plate, don’t take lid off in open air)

Question 26

How are dermatophyte infections treated if they’re in the skin?

Answer 26

If they don’t involve hair or nails, topical antifungals (azoles, terbinafine) are effective.

For chronic skin infections involved T. rubrum, oral antifunal agents )griseofulvin, azoles, and terbinafine) may be needed.

Question 27

How are dermatophyte infections treated if they involve hair and nails?

Answer 27

Oral antifungals agents such as griseofulvin, azoles, and terbinafines.

Jublia is a new azole for treatment of onychomycosis. Topical antifunal that needs to be applied once per day for 48 wks. Superbowl commercial with phil simms, deon sanders, and howie long.

Question 28

For infections of the nail _______ can be used?

Answer 28

Pinpoint laser therapy.

Question 29

What infection is sporothrix schenckii responsible for? How does innoculation occur?

Answer 29

Lymphocuteaneous sporotrichosis.

Inoculation occurs through traumatic introduction through the dermic, most common subcuteaneous mucoses in the US.

Question 30

What is the morphology of sporothrix schenckii?

Answer 30

Thermally dimorphic fungus.

Mold at room temp (mold in the cold), and yeast at body temp (yeast in the heat).

Question 31

What clinical syndromes are associated with sporothrix schenckii?

Answer 31

Site of inoculation if non or mildly painful and will appear as a nodular lesion that will eventually ulcerate.

Infection can spread through lymphatics that drain the site and a series of linear nodules will appear.

Question 32

How would you diagnose sporothrix schenckii?

Answer 32

Since the yeast form is rarely observed in human histological preparations, culturing leads to the more definitive diagnosis.

Incubating plate at room temp will result in mold growing.

Incubating plate at 37 degrees will lead to the growth of yeast.

Question 33

What is the treatment of sporothrix schenckii?

Answer 33

Itraconazole is safe and effective, but it must be administered for a long period of time (3-6 months).

Question 34

A 4 yo boy was taken by his mother to the family doc for a 2 month old growing bump on the back of his head. He had no other siblings or pets. He attended a dar care center on weekdays. Exam revealed a child in no distress. He has a scaling lesion 3.5 cm in diameter with pinpoint pustules was present on he posterior of his scalp. A KOH prep was negative. A fungal culture from the lesion was positive for a fungus with numerous microcinidia typical of microsporium species. What is the human niche where this organism best proliferates?

Answer 34

Cells enriched with keratin such as those found in the hair skin and nails.

Question 35

What can be seen under wood light (black light) that looks like tinea crursis but isn’t?

Answer 35

Erythrasma, caused by corynebacterium minutissimum.

This is a bacterial infection and can be treated with Erythromycin.