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dermatophytosis
Superficial fungus infection of the skin, hair &/or nails (keratinized tissue) including:
1) Tinea: Tinea facialis, Tinea corporis, Tinea cruris, Tinea pedis, Tinea capitis, Tinea barbae
2) dermatophytic folliculitis
3) Majocchi's granuloma
4) onychomycosis
Etiology:
1) Dermatophytes (more than 40 species recognized)
a) Epidermophyton
b) Microsporum
c) Trichophyton
2) immunosuppression is a predisposing factor
Epidemiology:
1) person to person or animal to person spread by fomites
2) contact with contaminated soil (less common)
Pathology:
1) organisms invade the stratum corneum, hair & nails
2) inflammation of the underlying layers of skin occurs
3) the degree of inflammation depends upon the host response to the organism
a) geophilic organisms produce the greatest response
b) anthrophilic organisms induce less inflammation
4) cell-mediated immunity & antimicrobial activity of polymorphonuclear leukocytes restrict dermatophyte pathogenicity
Clinical manifestations:
1) inflammation in the epidermis & upper dermis resembles eczema
2) distinguishing feature is sharp, scaly borders with central clearing
3) areas with a high concentration of sebaceous glands are most commonly affected [3]
4) pruritic, peripheral annular, erythematous eruption with peripheral scaling, expanding outward as concentric rings (Tinea corporis)
Laboratory:
1) microscopic examination of a scale from the border of an active lesion using 10% KOH* shows septate hyphae
2) culture of skin scraping on fungal media
a) Sabouraud's dextrose agar
b) dermatophyte test medium
3) collect using #15 blade scalpel or edge of microscope slide
4) fungi best demonstrated with PAS or methenamine silver
* chlorazol black solution may used instead of KOH [3]
Differential diagnosis:
- cutaneous candidiasis [3]
a) microscopic exam with KOH shows budding yeast or short non septate hyphae
b) cutaneous candidiasis of the scrotum is common, Tinea infections of the scrotum are rare
c) satellite lesions are classic for cutaneous candidiasis
- Tinea versicolor also shows short hyphae & yeast forms [3]
Management:
1) topical antifungal agents (over the counter) [3]
a) indications
- superficial dermatophytosis not involving nails, hair follicles or scalp
b) OTC antifungal agents
- miconazole
- clotrimazole
- terbinafine
c) avoid topical glucocorticoids [3]
2) systemic agents
a) indications:
- tinea capitis & tinea unguium (onychomysosis)
- extensive tinea corporis
- topical treatment-resistant dermatophytosis
b) systemic antifungals
- terbinafine
- itraconazole
- ketoconazole
- griseofulvin
3) see specific agents
Related
Dermatophyte
fomite
Specific
onychomycosis
Tinea
General
mycosis; fungal infection
figurate dermatitis (rings, arcs)
References
- Saunders Manual of Medical Practice, Rakel (ed), WB Saunders,
Philadelphia, 1996, pg 919
- Color Atlas & Synopsis of Clinical Dermatology, Common
& Serious Diseases, 3rd ed, Fitzpatrick et al, McGraw Hill, NY,
1997, pg 688-691
- Medical Knowledge Self Assessment Program (MKSAP) 14, 15, 16,
17. American College of Physicians, Philadelphia 2006, 2009,
2012, 2015.