Fungal Infections of the Skin Flashcards
Where do fungi live?
Dead, horny outer layer, penetrate only the stratum corneum aka surface layer of skin. Fungi infect the skin, hair, and nails.
Fungus can be found on humans, animals, and in the soil.
What diseases are caused by fungi?
tinea, tinea versicolor, and candidiasis (yeast infection)
Causes of fungal infection
warm, moist, occluded environments
family history
compromised immune system
Dermatophytes
Grows only on or within keratinized structures.
tinea capitis
fungal infection of the scalp
age 3 - 9 mostly
disproportionally African American
15% infected has cross-infection with tinea corporis
very contagious
SX impetigo-like lesions with crusting and redness, inflamed, scaly, gray patch type plaques alopecia, tender and pustular nodules.
in severe cases and painful in a child, prednisone (Deltasone) 1 mg/kg/d for 3 to 4 days given to child pt
tinea corporis
“Ringworm” it affects the face, limbs, and trunk,
but NOT the groin, hands, or feet
SX ring-shaped lesion with well-demarcated margins, central clearing, scaly, erythematous border
commonly transmitted from infected mats in wresting or martial arts
tinea cruris
“Jock itch”, affects groin and inguinal folds, but not the scrotum;
SX large lesions, erythematous, well-demarcated and peripherally spreading, macular and with central clearing
hallmark sx pruritus or burning sensation
often accompanied by fungal infection of the feet
tinea pedis
“Athlete’s foot”, affects web spaces between toes, sometimes toes or instep
SX scaling, itching, denudation, sodden maceration, vesicles, thickness and cracking of epidermis on the sole, heel, side of foot.
tinea unguium
Onychomycosis; fungal infection of the nail;
usually asymptomatic but is portal of entry for more serious bacterial infection;
onycholysis - separation of the nail from the nail bed;
scaly with subungual debris;
when untreated, nail thickens and turns yellowish brown.
How to prevent fungal infections
Apply powder containing miconazle (Monistat) or tolnaftate (Tinactin) after bathing, dry completely with hair dryer on low heat.
Drug therapy for fungal infections
Topical TX for most fungal infections except tinea capitis and tinea unguium.
Types of antifungals
topical azoles
topical allylamine
griseofulvin
systemic azoles
systemic allylamine
Topical azole antifungals
TX tinea corporis, tinea cruris, tinea pedis, cutaneous candidiasis
RX ketoconazole (Nizoral) - not for sulfite sensitive pt, clotrimazole (Lotrimin), miconazole (Monistat, Micatin)
applied BID for 2 to 4 weeks, and continued for 1 more week after lesions clear
CX pregnancy or lactation
caution in pt with hepatocellular failure (liver failure)
AX stinging, irritation, pruritis, erythema
Topical allylamine antifungals
TX dermatophyte infections, NOT yeast (tinea versicolor and candidiasis)
RX terbinafine (Lamisil) - CX sun exposure or tanning beds, children, occlusive dressing, mucous membranes; and naftifine (Tinactin) - CX children < 2 yo (but NOT tolnaftate)
AX burning, irritation, dry skin, skin exfoliation
Order of tx for tinea corporis, tinea cruris, and tinea pedis
1st line
topical azole antifungals 2 to 4 weeks including an additional 2 weeks after rash is gone
2nd line systematic therapy (PO) usually with terbinafine or fluconazle.
griseofulvin
Systemic (PO) antifungal
CX pregnancy, prophyria, hepatic failure
AX HA, n/v/d, photosensitivity, alcohol use
RX
aggravate lupus
increase warfarin levels
decrease barbiturates and cyclosporine levels
decrease oral contraceptive effectiveness
bad reaction with alcohol
Order of tx for tinea capitis
1st line
griseofulvin for 8 weeks
2nd line
terbinafine for 4 weeks
Order of tx for tinea unguium (onychomycosis)
1st line
PO itraconazle for 12 weeks
2nd line
terbinafine for 12 weeks
Systemic allylamine antifungals
TX tinea unguium
AX diarrhea, dyspepsia, rash, liver failure (check ALT and AST prior TX and at 6 - 8 wks), HA
RX terbinafine (Lamasil)
terbinafine is potentiated by cimetidine (Tagamet) and antagonized by rifampin (Rifadin), check level of cyclosporine if taking both terbinafine and cyclosporine.
Systemic azole antifungals
TX tinea capitis, tinea unguium
pulse dosing due to long half-life
CX pregnancy, pt on quinidine
RX fluconazole (Diflucan)
AX GI upset, rash, fatigue, hepatic dysfunction, edema, hypokalemia
fluconazole (Diflucan) level increases when given with hydrochlorothiazide (Hydrodiuril)
systemic azole potentiates hypoglycemic drugs, triazolam (Halcion), midazolam (Versed), and warfarin
avoid taking systemic azole within 2 hours of taking anticholinergics, histamine-2 blockers, and antacids as they inhibit absorption of systemic azoles
tinea versicolor - what is it?
opportunistic superficial yeast infection.
Characteristics of tinea versicolor
chronic, asymptomatic infection characterized by well-demarcated, scaling patches of varied coloration from whitish to pink, tan, or brown
Causes of tinea versicolor
moist skin surfaces
common in physically active people
common in summer months
SX of tinea versicolor
round or oval macules
overlay of scales that may group together to form larger patches
found on trunk, upper arms, and neck
mild itching
confirmed by KOH test positive
