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Tinea pedis (athlete's foot)

Fungal infection of the feet. Etiology: 1) general a) Trichophyton rubrum (most common cause of chronic Tinea pedis) b) Trichophyton mentagrophytes causes more inflammatory lesions c) Aspergillus spp [5] 2) interdigital type a) dermatophytes - Trichophyton mentagrophytes - Trichophyton rubrum - Epidermophyton floccosum b) non-dermatophytes - Candida albicans - Scytalidium hyalinum - Hendersonula toruloidea 3) moccasin type a) Trichophyton rubrum b) Epidermophyton floccosum 4) vesicular, inflammatory or bullous - Trichophyton mentagrophytes 5) ulcerative a) Trichophyton mentagrophytes b) Trichophyton rubrum c) Epidermophyton floccosum 6) predisposing factors: a) hot, humid weather b) occlusive footwear c) excessive sweating d) diabetes mellitus [4] Epidemiology: 1) most frequent form of cutaneous fungal infection 2) males > females 3) most common ages 20-50 years 4) acquired by walking barefoot on contaminated floors Clinical manifestations: 1) 3 common forms a) interdigital - macerated, red & scaly toe web space - often associated with fissures - 4th web space is most commonly affected b) moccasin type - dry, thick, scaly skin on soles & sides of feet - erythematous soles - may be seen on 2 feet & 1 hand, or 1 foot & 2 hands - case with fungal rash extending to include lateral malleolus [4] - chronic form c) vesicular, inflammatory or bullous - erythema, scaling & vesicles, usually of the instep - 1-2 mm vesicles may be very pruritus (acute form) - vesicles may coalesce into larger bullae 2) less common forms a) ulcerative - an extension of interdigital type into dermis due to maceration & secondary bacterial infection 3) dermatophytid a) vesicular eruption of the fingers &/or palmar aspects of the hands b) inflammatory response c) secondary bacterial infection may occur 3) infection tends to be chronic with exacerbations in hot weather * images [7] Laboratory: (see Tinea) Complications: - may provide portal of entry for cellulitis or lymphangitis in patients with chronic leg edema, especially after harvesting of leg veins for CABG Differential diagnosis: - plantar wart (no erythema, no maceration, plaque vs scaly, may be covered with callus) [9] Management: 1) topical imidazole compound for 4 weeks a) effective in treating dermatophyte, Candida & Malassezia infection b) clotrimazole# (Lotrimin AF) c) miconazole# (Monistat, Lotrimin AF) d) ketoconazole (Nizoral) e) econazole (Spectazole) f) sulconazole (Exelderm) g) oxiconazole (Oxistat) h) terconazole (Terazol) i) butenafine* (Lotrimin Ultra) [3] j) terbinafine (Lamisil) 2) topical povidone iodine (Betadine) for initial management of severe cases 3) oral antifungals a) griseofulvin (ultramicrosize) 250-375 mg BID for 4-8 weeks b) fluconazole 150 mg/week for 4 weeks c) itraconazole 100 mg/day for 4 weeks 4) patient education a) avoid occlusive footwear b) wear shower shoes in public showers c) high-temperature (>= 60 degrees C) laundering of socks is needed for eradication of Trichphyton rubrum & Aspergillus species causing Tinea pedis [5] * fungicidal agent # fungistatic agent

General

Tinea

References

  1. Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 997-1000
  2. Color Atlas & Synopsis of Clinical Dermatology, Common & Serious Diseases, 3rd ed, Fitzpatrick et al, McGraw Hill, NY, 1997, pg 692-695
  3. Prescriber's Letter 9(2):11 2002
  4. Medical Knowledge Self Assessment Program (MKSAP) 16, 17, 18, 19. American College of Physicians, Philadelphia 2012, 2014, 2018, 2022 - Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022
  5. Amichai B et al. The effect of domestic laundry processes on fungal contamination of socks. Int J Dermatol 2013 Nov; 52:1392 PMID: 23879806
  6. Robbins CM, Elston DM (images) Medscape: Tinea Pedis http://emedicine.medscape.com/article/1091684-overview
  7. DermNet NZ. Tinea pedis (images) http://www.dermnetnz.org/fungal/tinea-pedis.html
  8. Levitt JO, Levitt BH, Akhavan A, Yanofsky H. The sensitivity and specificity of potassium hydroxide smear and fungal culture relative to clinical assessment in the evaluation of tinea pedis: a pooled analysis. Dermatol Res Pract. 2010;2010:764843. Epub 2010 Jun 22. PMID: 20672004 Free PMC Article
  9. NEJM Knowledge+ Dermatology