Fungal Infections/Ringworm

Question 1

Types of fungal infections

Answer 1

• Tina corporis: any part of body except hands, feet, scalp, face, groin, nails* Tinea cruris: groin and inner thighs -> warm and moist areas* Tinea facei: face (not at bear or moustache area)* Tinea manuum: hands* Tinea pedis/athletes foot: feet or btw toes* Tinea unguium: nails* Trench foot: feet soacked in wet condition for long periods

Question 2

What are dermatophytic infections?

Answer 2

Contagious, transmitted directly from one host to another, invade stratum corneum of skin/hair/nails - generally not living tissue, grows in keratinised layer of epidermis

Question 3

Distribution areas of dermatophytic infections

Answer 3

Head, front of arms, groin area, front of feet. Areas of body that tend to be warm and contain moisture (ideal for growth)

Question 4

Diagnosis and differential diagnosis of dermatophytic infections

Answer 4

• age and sex: athelete foot most prevalent in adolescents and young adults, esp males. Nail involvement usually in older adults.- presence of itch: fungal infections cause itch, irritation or burning sensation (this eliminates psoriasis but not dermatitis)- associated smx: fungal infections tend to be dry and scaly (except athelete foot) and have a sharp margin btw infected and noninfected skin.- previous and fam hx: fungal infections usually acute in onset with no previous episodes, although athlete foot may become recurrent. Positive fam hx of dermatitis or psoriasis should influence differential diagnosis.

Question 5

Smx and clinical presentation of tinea pedis/athlete foot

Answer 5

• often self diagnosed- itching, flaking/scaly skin btw toes- can be dry or moist or weeping- can spread to sole or instep (arched part of top of foot btw toes and ankle)- most cases are mild- if skin breaks, can lead to sec bacterial infection- may spread to nails causing nail infection- contagious, spread through swimming pools/changing rooms, use of same facilities

Question 6

What is trench foot?

Answer 6

Prolonged exposure of feet to cold water. Note: not every infection of the foot is tinea pedis

Question 7

Clinical presentation and smx of tinea corporis

Answer 7

• infection of skin that doesnt involve the face, hands, feet, groin or scalp- itchy, red scaly patches with well defined border- single or multiple lesions which may overlap- central clearing (centre of lesion is clear)

Question 8

Clinical presentation of tinea cruris

Answer 8

• red, scaling w raised borders at groin area- scrotum and penis is often not infected- pustules, vesicles, mascerations found along the borders, where infection is spreading along the edges

Question 9

Non-pharm management of tinea cruris

Answer 9

• dry groin carefully after bathing using a separate towel- do not share towels, sheets or personal clothing- avoid wearing occlusive or synthetic clothing- if overweight, try to loss weight to reduce chafing and sweating- treat the feet if tinea pedis present (can occur concurrently with tinea cruris)

Question 10

Clinical presentation of tinea facei

Answer 10

• rare- round, oval , scaling patches- aggravated by sun exposure

Question 11

Clinical presentation of tinea manuum

Answer 11

• dryness of hand

Question 12

Overview treatment of mycotic infections of skin (some examples)

Answer 12

Tinea pedia: naftifine cream daily, fluconazole PO 150mg per week for 1-4wksTinea manuum: ketoconazole 200mg daily x 4wksTinea cruris: Clotrimazole BD, naftifine cream daily, itraconzaole 200-400mg/day x 1wkTinea corporis: miconazole BD, naftifine cream daily, terbinafine BD, tolnaftate BD, terbinafine 250mg/day x 2wks

Question 13

What are the main classes of antimycotic drugs?

Answer 13

• benzoic acid- tolfnaftate- azole- allylamine

Question 14

What is the use of tolnaftate (eg. tolnaderm cream)

Answer 14

• for tinea cruris, corporis and pedis)- apply BD for up to 2-3wks. Additional 2-3wks after smx resolve- safe in all pt grps- may sting slightly when applied to skin

Question 15

What is the use of azoles (TOP)?

Answer 15

• MOA: inhibitions of ergosterol synthesis- eg. clotrimazole, miconazole, ketoconazole- duration topical use typically 2-4wks and continue 1 wk after resolution of smx- antifungal and antibacterial action- rarely irritation on topical application

Question 16

What is the use of oral azole drugs as system antifungal therapy?

Answer 16

• eg. fluconazole (triazole), ketoconazole (imidazole) and itraconazole (triazole)- fluconazole is highly water solubleitraconazole is very lipophilic, good for nail infection- system antifungal therapy licenssed for tinea cruris, manuum and pedis as these infections may not respond to TOP azole therapy

Question 17

What is the use of allylamine antifungals?

Answer 17

• cure rate the same as for imidazoles but more effective in preventing recurrence (fungicidal and fungistatic activity)- eg. naftifine, terbinafine- for children >16y/o

Question 18

When to refer for dermatophytic infections?

Answer 18

• signs of bacterial infection- suspected scalp of facial involvement- unresponsive to pharmacist supervised treatment for 4wks (might be due to DM)- DM patients

Question 19

Non pharm management of athletes foot

Answer 19

1. dry skin thoroughly after showering. do not share towels2. wear cotton socks and change at least once a day3. avoid use of occlusive nonbreathable shoes4. dust shoes and socks with antifungal powder5. avoid scratching infected skin6. use flip flops when using communal changing rooms

Question 20

What is the use of steroid containing prdts for dermatophytic infections?

Answer 20

• max period of tx is 7days. this limits usefulness as fungal infections take >7days to clear esp because prdts need to be used after lesions have cleared to prevent reinfection- best used to control initial smx of redness and itch before switching to and imidazole-only prdt after initial 7d tx

Question 21

Epidemiology and etiology of onychomycosis

Answer 21

• prevalence of 10-30% of general pop.- affected nails can disrupt integrity of surrounding skin and potentially increase the rick of sec bacterial infections- dermatophytes are the most freq cause of onychomycosis- dull opaque or yellow nail, thickens and distorts, then brittle, crumbles and falls off, mainly big toe

Question 22

Progressive steps of tinea unguium to complete nail destruction

Answer 22

1. Lateral onychomycosis: white or yellow opaque streak appears at one side of nail2. subungual hyperkeratosis: scaling under nail, spread to underneath nail3. Distal onycholysis: separation of nail from nail bed. end of nail lifts, free edge often crumbles4. superficial white onychomycosis: white spots on nail, flaky white patches and pits appear on top of nail plate5. proximal onychomycosis: yellow spots appear in half-moon (lunula)6. complete destruction of nail

Question 23

Differential diagnosis of fungal nail infections

Answer 23

• psoriasis- lichen planus- periungual squamous cell carcinoma- yellow nail syndrome- trauma

Question 24

Clinical features of nail psoriasis

Answer 24

Psoriasis can enhance the speed of nail growth and thickness of the nail plate.* Pitting is a sign of partial loss of cells from the surface of the nail plate. It is due to psoriasis in the proximal nail matrix. Pitting: little depressions in nails* Leukonychia (areas of white on the nail plate) is due to parakeratosis within the body of the nail plate and is due to psoriasis in the mid-matrix.* Onycholysis describes the separation of the nail plate from the underlying nail bed and hyponychium. The affected distal nail plate appears white or yellow.* Oil drop or salmon patch is a translucent yellow-red discolouration in the nail bed proximal to onycholysis. It reflects inflammation and can be tender.* Subungual hyperkeratosis is scaling under the nail due to excessive proliferation of keratinocytes in the nail bed and hyponychium.* Transverse lines and ridges are due to intermittent inflammation, causing growth arrest followedby hyperproliferation in the proximal nail matrix. The lines and ridges move out distally as the nail grows

Question 25

Topical pharmacotherapy for onychomycosis

Answer 25

Amorolfine 5% nail lacquer: for fingernails- weekly for 6m. for toenails- weekly for 9-12m.TOP only useful for infection till step 3

Question 26

Gold standard therapy for onychomycosis

Answer 26

oral terbinafine: 250mg daily for 6wks for fingernails and 12wks for toenails

Question 27

Dosing for Pulse therapy of itraconazole (imidazole) for oral therapy for onychomycoses

Answer 27

Fingernails: 200mg BD one wk per month for 2monthsToenails: 200mg daily for 12wks