Fungal Infections Flashcards
What are dermatophytes?
Dermatophytes are a group of fungi capable of causing infection to hair, skin and nails
3 genera of dermatophytes?
- trichophyton
- epidermophyton
- microsporum
Classification of dermatophytes?
- Anthropophilic dermatophytes
- only grow on human skin, hair and nails - Geophilic dermatophytes
- live in soil but may infect humans - Zoophilic dermatophytes
- originate from animals but may infect humans
NOTE; In general geophilic and zoophilic infections elicit brisk inflammatory response, anthropophilic infections are milder
Names of clinical fungal infections?
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
Describe tinea capitis?
- 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
Types of tinea capitis infection?
- Endothrix infection
- Fungus confined in the hair shaft - Ectothrix infection
- some of hyphae break through to grow exterior to hair shaft
Types of tinea capitis based on clinical appearance?
- seborrhoeic dermatitis-like
- black dot type
- inflammatory type
Seborrheic dermatitis like tinea capitis?
diffuse scaling with or without patches of hair loss
Black dot type tinea capitis?
well defined areas of hair loss, with hairs broken off at the follicular orifice scalp broken scalp hairs leaving behind black dots
Inflammatory type tinea capitis?
- pustular - abscesses,
- kerion - edematous nodules with or without pustules
- favus - crusts in which hairs are matted together with dermatophytes and debris
Characteristic appearance of tinea capitis?
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
Describe tinea of the hand?
- 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
Describe tinea unginum?
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)
Describe tinea crusis?
- 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
What is intertrigo?
- 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
What is tinea incognito?
Alteration of characteristic features of tinea lesion after application of corticosteroids.
- Less but uniform scaling, less pronounced borders, pustules
Diagnosis of Tinea?
- Usually clinical.
- KOH examination of scrapings from the active edge of the lesion.
- Fungal culture may be required especially for scalp infection.
T. Corporis, faciei, cruris, treatment?
- Topical treatment is first line of therapy
- 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 - 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)
Treatment for T.Capitis and T.Barbae?
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.
Alternative treatment for T.Capitis and T.Barbae?
- Fluconazole 6mg/kg/dy for 20 days
- Itraconazole 5mg/kg/day 4-6 weeks.
- 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
Treatment for T.Unguim?
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
Describe pityriasis versicolor?
- 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.
Predilection sites for pityriasis versicolor?
- Primarily affects upper trunk, neck, upper arms; may coalesce to affect large body surface.
- Face, back of hands and legs can be affected
Pathogenesis of pityriasis versicolor?
- Melassezia, cause of P. Versicolor is normal commensal on the skin.
- Disease occurs when it changes from yeast (budding), to mycelial (filamentous) form
