Fungal Infections

Question 1

What are dermatophytes?

Answer 1

Dermatophytes are a group of fungi capable of causing infection to hair, skin and nails

Question 2

3 genera of dermatophytes?

Answer 2

1. trichophyton
2. epidermophyton
3. microsporum

Question 3

Classification of dermatophytes?

Answer 3

1. Anthropophilic dermatophytes
   - only grow on human skin, hair and nails
2. Geophilic dermatophytes
   - live in soil but may infect humans
3. Zoophilic dermatophytes
   - originate from animals but may infect humans
   NOTE; In general geophilic and zoophilic infections elicit brisk inflammatory response, anthropophilic infections are milder

Question 4

Names of clinical fungal infections?

Answer 4

Clinical infections are named for the area of the body infected:
1. Tinea capitis: hair of the scalp
2. Tinea barbae: hair of face and neck
3. Tinea corporis: trunk and limbs (minus palmar/plantar, interweb skin) body
4. Tinea faciei: non hair bearing area of the face
5. Tinea cruris: groin
6. Tinea pedis: plantar and in between toes
7. Tinea manuum: palm and interweb
8. Tinea unguium (Onychomycosis): nails

Question 5

Describe tinea capitis?

Answer 5

• Predominant in children 3-7 years of age
• Infection originates from contact with a pet or an infected person
• Spores are shed in the air in the vicinity of the patient, fallen hairs, formites, furniture hence direct contact not necessary for transmission
• Large family size, crowding and low social economic status increase chances of infection
• Asymptomatic carriage by schoolmates and adults is an important factor precipitating infection

Question 6

Types of tinea capitis infection?

Answer 6

1. Endothrix infection
   - Fungus confined in the hair shaft
2. Ectothrix infection
   - some of hyphae break through to grow exterior to hair shaft

Question 7

Types of tinea capitis based on clinical appearance?

Answer 7

1. seborrhoeic dermatitis-like
2. black dot type
3. inflammatory type

Question 8

Seborrheic dermatitis like tinea capitis?

Answer 8

diffuse scaling with or without patches of hair loss

Question 9

Black dot type tinea capitis?

Answer 9

well defined areas of hair loss, with hairs broken off at the follicular orifice scalp broken scalp hairs leaving behind black dots

Question 10

Inflammatory type tinea capitis?

Answer 10

1. pustular - abscesses,
2. kerion - edematous nodules with or without pustules
3. favus - crusts in which hairs are matted together with dermatophytes and debris

Question 11

Characteristic appearance of tinea capitis?

Answer 11

Very characteristically, there is an active border of inflammation that is scaly, red, raised with ↑hyphae
- Vesicle may appear if inflammation is intense at the border

Question 12

Describe tinea of the hand?

Answer 12

• May be asymptomatic, with patient unaware of infection, attributing changes to hard physical work.
• May involve one hand and two feet or two feet and one hand

Question 13

Describe tinea unginum?

Answer 13

3 patterns based upon point of fungal entry into the nail unit
1. Distal/lateral subungual infection
- via hyponychium
2. Superficial spreading infection
- direct nail plate invasion
3. Proximal subungual
- under proximal fold (in the immunocompromised)

Question 14

Describe tinea crusis?

Answer 14

• Manifest as half-moon-shaped plaque with well-defined scaling and an advancing border out of the crural fold > Usually unilateral
• Infection may migrate to buttock and gluteal area
• Common in summer after sweating, wearing wet clothing
• Always look for tinea pedis in patients with T cruris as infection may start from the foot

Question 15

What is intertrigo?

Answer 15

• red, half-moon shaped plaque like t.cruris
• forms after moisture accumulates in the crural fold where 2 borders of apposed skin surface meet
• Besides fungus, there may be candida, bacterial colonisation

Question 16

What is tinea incognito?

Answer 16

Alteration of characteristic features of tinea lesion after application of corticosteroids.
- Less but uniform scaling, less pronounced borders, pustules

Question 17

Diagnosis of Tinea?

Answer 17

1. Usually clinical.
2. KOH examination of scrapings from the active edge of the lesion.
3. Fungal culture may be required especially for scalp infection.

Question 18

T. Corporis, faciei, cruris, treatment?

Answer 18

1. Topical treatment is first line of therapy
2. antifungal creams
   e.g. miconazole, clotrimazole, terbinafine creams B.D for at least 14 days, but treatment must be continued for a wk after lesions heal
3. Mild topical corticosteroid may be added for a few days for very inflammed lesions
   Note: Systemic treatment may be given for very extensive or non responding disease like in T capitis but shorter (2 to 4 weeks)

Question 19

Treatment for T.Capitis and T.Barbae?

Answer 19

Topical therapy alone not an option as fungus is unreachable deep in the hair follicles so tinea of hair follicles must get systemic treatment
1. Griseofulvin 20-25mg/kg for 6-8 wks
- most recommended treatment, drug safe
- Better absorption if taken with fatty meal
2. For inflammatory lesions, systemic steroids in the first 3 to 4 weeks can result in rapid resolution of symptoms and minimise scarring if started early.

Question 20

Alternative treatment for T.Capitis and T.Barbae?

Answer 20

1. Fluconazole 6mg/kg/dy for 20 days
2. Itraconazole 5mg/kg/day 4-6 weeks.
3. Terbinafine:
   - Weight 10-20 kg 62.5 mg/d 2-4 wk
   - Weight 20-40 kg 125 mg/d 2-4 wk
   - Weight >40 kg 250 mg/d 2-4 wk

Question 21

Treatment for T.Unguim?

Answer 21

1.Treatment must be continued ranging from 9 months (finger nails) to 18-24 months (toenails).
2. Other preventive measures
- anti-fungal/anti-absorbent powders
- frequent nail clipping
- discarding or treating old shoes with antifungal powders

Question 22

Describe pityriasis versicolor?

Answer 22

• Characterised by scaly hypo-, hyperpigmented macules.
• Asymptomatic, and a cosmetic concern for most people, though some may experience mild itch.
• Common in adolescence & young adulthood.
• Not a marker of HIV infection.

Question 23

Predilection sites for pityriasis versicolor?

Answer 23

• Primarily affects upper trunk, neck, upper arms; may coalesce to affect large body surface.
• Face, back of hands and legs can be affected

Question 24

Pathogenesis of pityriasis versicolor?

Answer 24

• Melassezia, cause of P. Versicolor is normal commensal on the skin.
• Disease occurs when it changes from yeast (budding), to mycelial (filamentous) form

Question 25

Predisposing factors for PV?

Answer 25

1. excess heat
2. humidity
3. malnutrition
4. burns
5. pregnancy
6. oral contraceptives
7. Believed to be non-contagious.

Question 26

Clinical features of PV?

Answer 26

1. Begin as multiple small macules that enlarge radially to coalesce into multiple oval to round patches or plaques with minimal scale.
2. Stretching the skin demonstrates the scale.
3. Lesions usually hypopigmented, but may be hyperpigmented in blacks

Question 27

Treatment for PV?

Answer 27

1. miconazole, clotrimazole cream BD for 4 weeks.
2. Ketokonazole shampoo 2 % 2x/wk: apply from scalp down to thighs, leave for 5 mins, then rinse off.
3. Selenium sulphide suspension 2.5 % (Selsun shampoo) daily for 10 mins for 2 - 4 weeks.
4. Salicylic acid 5 % gel overnight for 2 - 4 weeks

Question 28

Treatment for PV if extensive or recurrent?

Answer 28

1. Ketokonazole 200mg OD for 5 days, or 400mg weekly for 2 weeks.
2. Itraconazole 200mg OD for 5-7 days
3. Fluconazole 300mg OD for 2 weeks.

Question 29

Treatment for PV for people at risk of frequent recurrences?

Answer 29

1. ketokonazole shampoo weekly as ‘soap’ or
2. Monthly dosing of one of ketokonazole 400mg, Itraconazole 400mg, Fluconazole 300mg.

Question 30

How long will hypopigmentation of PV last?

Answer 30

Hypopigmentation may take a while to resolve
- Stretch skin to assess if fungus still present after treatment.