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Toronto Notes 2019
Infections
Dermatology D27
Table 18. Different Manifestations of Dermatophyte Infection
Tinea Capitis
Tinea Corporis
(Ringworm)
Tinea Cruris
(“Jock Itch”)
Tinea Pedis
(Athlete’s Foot)
Tinea Manuum
Tinea Unguium
(Onychomycosis)
Clinical Presentation
Round, scaly patches of alopecia, possibly with broken off hairs; pruritic
Sites: scalp, eyelashes, and eyebrows; involving hair shafts and follicles
Kerion (boggy, elevated, purulent inflamed nodule/ plaque) may form secondary to infection by bacteria and result in scarring
May have occipital lymphadenopathy
Affects children (mainly black), immunocompromised adults
Very contagious and may be transmitted from barber, hats, theatre seats, pets
Pruritic, scaly, round/oval plaque with active erythematous margin, ± central clearing Sites: trunk, limbs, face
Scaly patch/plaque with a well-defined, curved border and central clearing
Pruritic, erythematous, dry/macerated
Sites: starts medial thigh, spreads centrifugally to perineum, gluteal cleft, buttocks
Pruritic scaling and/or maceration of the web spaces, and powdery scaling of soles
Acute infection: interdigital (especially 4th web space) red/white scales, vesicles, bullae, often with maceration Secondary bacterial infection may occur
Chronic: non-pruritic, pink, scaling keratosis on soles, and sides of feet
May present as flare-up of chronic tinea pedis Predisposing factors: heat, humidity, occlusive footwear
Primary fungal infection of the hand is rare; usually associated with tinea pedis
Acute: blisters at edge of red areas on hands Chronic: single dry scaly patch
Crumbling, distally dystrophic nails; yellowish, opaque with subungual hyperkeratotic debris
Toenail infections usually precede fingernail infections T. rubrum (90% of all toenail infections)
Differential Diagnosis
Alopecia areata, psoriasis, seborrheic dermatitis, trichotillomania
Granuloma annulare, pityriasis rosea, psoriasis, seborrheic dermatitis
Candidiasis (involvement of scrotum and satellite lesions), contact dermatitis, erythrasma
AD, contact dermatitis, dyshidrotic dermatitis, erythrasma, intertrigo, inverse psoriasis
AD, contact dermatitis, granuloma annulare, psoriasis
Psoriasis, lichen planus, contact dermatitis, traumatic onychodystrophies, bacterial infection
Investigations
Wood’s light examination of hair: green fluorescence only for Microsporum infection
Culture of scales/hair shaft Microscopic examination of KOH preparation of scales or hair shafts
Microscopic examinations of KOH prep of scales shows hyphae Culture of scales
Same as for tinea corporis
Same as for tinea corporis
Same as for tinea corporis
Microscopic examinations of KOH prep of scales from subungual scraping shows hyphae
Culture of subungual scraping or nail clippings on Sabouraud’s agar PAS stain of nail clipping by pathology
Management
Terbinafine (Lamisil®) x 4 wk
NB: oral agents are required to penetrate the hair root where dermatophyte resides
Adjunctive antifungal shampoos or lotions may be helpful, and may prevent spread (e.g. selenium sulfide, ketoconozole, ciclopirox)
Topicals: 1% clotrimazole, 2% ketoconazole
2% miconazole, terbinafine or ciclopirox olamine cream bid for 2-4 wk
Oral terbinafine, or itraconazole, or fluconazole, or ketoconazole if extensive
Same as for tinea corporis
Same as for tinea corporis
Same as for tinea corporis
Terbinafine (Lamisil®) (6 wk for fingernails, 12 wk for toenails) Itraconazole (Sporanox®) 7 d on, 3 wk off (2 pulses for fingernails, 3 pulses for toenails)
Topical: ciclopirox (Penlac®); nail lacquer (often ineffective), Efinaconazole (Jublia®) (48 wk)
Parasitic Infections
SCABIES
Clinical Presentation
• characterizedbysuperficialburrows,intensepruritus(especiallynocturnal),andsecondaryinfection
• primarylesion:superficiallinearburrows;inflammatorypapulesandnodulesintheaxillaandgroin
• secondarylesion:smallurticarialcrustedpapules,eczematousplaques,excoriations
• commonsites:axillae,groin,buttocks,hands/feet(especiallywebspaces),sparingofheadandneck(exceptininfants)
Pathophysiology
• scabiesmiteremainsalive2-3donclothing/sheets • incubationof1mo,thenpruritusbegins
• re-infectionfollowedbyhypersensitivityin24h
Etiology
• Sarcoptesscabiei(amite)
• riskfactors:sexualpromiscuity,crowding,poverty,nosocomial,immunocompromised
Differential Diagnosis
• asteatoticeczema,dermatitisherpetiformis,lichensimplexchronicus(neurodermatitis)