dermatophytosis
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Introduction
Superficial fungus infection of the skin, hair &/or nails (keratinized tissue) including:
- Tinea: Tinea facialis, Tinea corporis, Tinea cruris, Tinea pedis, Tinea capitis, Tinea barbae
- dermatophytic folliculitis
- Majocchi's granuloma
- onychomycosis
Etiology
- Dermatophytes (more than 40 species recognized)
- immunosuppression is a predisposing factor
Epidemiology
- person to person or animal to person spread by fomites
- contact with contaminated soil (less common)
Pathology
- organisms invade the stratum corneum, hair & nails
- inflammation of the underlying layers of skin occurs
- the degree of inflammation depends upon the host response to the organism
- geophilic organisms produce the greatest response
- anthrophilic organisms induce less inflammation
- cell-mediated immunity & antimicrobial activity of polymorphonuclear leukocytes restrict dermatophyte pathogenicity
Clinical manifestations
- inflammation in the epidermis & upper dermis resembles eczema
- distinguishing feature is sharp, scaly borders with central clearing
- areas with a high concentration of sebaceous glands are most commonly affected[3]
- pruritic, peripheral annular, erythematous eruption with peripheral scaling, expanding outward as concentric rings (Tinea corporis)
Laboratory
- microscopic examination of a scale from the border of an active lesion using 10% KOH* shows septate hyphae
- culture of skin scraping on fungal media
- Sabouraud's dextrose agar
- dermatophyte test medium
- collect using #15 blade scalpel or edge of microscope slide
- fungi best demonstrated with PAS or methenamine silver
* chlorazol black solution may used instead of KOH[3]
Differential diagnosis
- cutaneous candidiasis[3]
- microscopic exam with KOH shows budding yeast or short non septate hyphae
- cutaneous candidiasis of the scrotum is common, Tinea infections of the scrotum are rare
- satellite lesions are classic for cutaneous candidiasis
- Tinea versicolor also shows short hyphae & yeast forms[3]
Management
- topical antifungal agents (over the counter)[3]
- indications
- superficial dermatophytosis not involving nails, hair follicles or scalp
- OTC antifungal agents
- avoid topical glucocorticoids[3]
- indications
- systemic agents
- indications:
- tinea capitis & tinea unguium (onychomysosis)
- extensive tinea corporis
- topical treatment-resistant dermatophytosis
- systemic antifungals
- indications:
- see specific agents
More general terms
More specific terms
Additional terms
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
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 Medical Knowledge Self Assessment Program (MKSAP) 14, 15, 16, 17. American College of Physicians, Philadelphia 2006, 2009, 2012, 2015.