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Toenail Onychomycosis: An Infectious Reservoir?
Graeme M. Lipper, MD
Factors Influencing Coexistence of Toenail Onychomycosis With Tinea Pedis and Other Dermatomycoses: A survey of 2761 Patients
Szepietowski JC, Reich A, Garlowska E, Kulig M, Baran E
Arch Dermatol. 2006;142:1279-1284
Summary
Onychomycosis accounts for roughly one half of all nail complaints evaluated by dermatologists.[1] In this prospective European study, Szepietowski and colleagues (the Onychomycosis Epidemiology Study Group) surveyed 241 dermatologists to identify a total of 2761 patients with toenail onychomycosis (mean age, 49 years; 54.9% female). Demographic and clinical data regarding these patients were gathered in Poland between September 2004 and April 2005.
All 2761 diagnoses of onychomycosis were confirmed by mycologic analysis (direct microscopic identification by KOH prep or positive Sabouraud agar culture), with dermatophytes being the most common fungal pathogen isolated (81.9%, most commonly Trichophyton rubrum). Additional pathogens included yeasts and molds. The surveyed dermatologists reported mean disease duration of 17.9 months, and the mean number of involved toenails was 4.4; the number of infected toenails correlated directly with disease duration. The majority of patients (75.4%) had bilateral toenail onychomycosis, and one third of cases were recurrent.
Almost half of the patients with toenail onychomycosis had concomitant fungal skin infections. These included:
tinea pedis (33.8%);
fingernail onychomycosis (7.4%);
tinea corporis (2.1%);
tinea manuum (1.6%); and
tinea capitis (0.5%)
Men with toenail onychomycosis were also more likely to have tinea cruris or tinea capitis compared with their female counterparts. Variables that increased the probability of concomitant fungal skin infections included a larger number of infected toenails, bilateral infection, longer duration of infection, and recurrence. Demographic variables associated with more widespread fungal infection included age older than 30 years, rural area of residence, and lower education level.
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Viewpoint
In this prospective analysis, the extent of toenail onychomycosis, duration of infection, and presence of recurrent disease were the 3 strongest predictors of fungal skin infections at other sites. As might be expected, tinea pedis was the most common site of concomitant fungal infection, followed by fingernail onychomycosis. Although caution should always be taken when extrapolating data from one geographic region (in this case, Poland) to another, comparable North American studies have revealed similar findings.[2,3] The investigators speculate that toenail onychomycosis represents an infectious reservoir from which distant sites can be seeded. Effective eradication of fungal pathogens such as dermatophytes from this "pedal reservoir"[4] may be the only way to prevent chronic fungal infections at other skin sites.
References
Roseeuw D. Achilles foot screening project: preliminary results of patients screened by dermatologists. J Eur Acad Dermatol Venereol. 1999;12(suppl 1):S6-S9.
Ghannoum MA, Hajjeh RA, Scher R, et al. A large-scale North American study of fungal isolates from nails: the frequency of onychomycosis, fungal distribution, and antifungal susceptibility patterns. J Am Acad Dermatol. 2000;43:641-648.
Foster KW, Ghannoum MA, Elewski B. Epidemiologic surveillance of cutaneous fungal skin infection in the United States from 1999-2002. J Am Acad Dermatol. 2004;50:748-752.
Daniel CR III, Jellinek NJ. The pedal fungus reservoir. Arch Dermatol. 2006;142:1344-1345.
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