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|Key=Onychomycosis, toenail, fingernail, infection, abscess |Description=Onychomycosis is a fungal infection of either the toe nail or fingernail. It is treated with some combination of oral or topical antifungals and may also require additional therapies. }}

Other Names

  • Onychomycosis
  • Toe Infection
  • Fungal Foot Infection


  • This page refers to Onychomycosis, a chronic fungal infection of the fingernail or toenail bed


  • Onychomycosis: derived from the Greek words "onyx" meaning nail and "mykes" meaning fungus[1]


  • Prevalence
    • Most common disorder affecting the nail unit and accounts for at least 50% of all nail disease[2]
    • Worldwide, approximately 5.5%[3]
    • North American and Europe: 4.3% in population based studies, 8.9% in hospital based studies[4]
    • Prevalence is rising, possibly due to longer life expectance, modern footwear, obesity, urbanization[5]
  • Demographics
    • Adults > children, prevalence increases with age[6]
    • In North America, the prevalence is about 0.4% in children[7], up to 35% in the elderly[8]
    • Toenail onychomycosis is more common in males, Candida fingernail onychomycosis is more common in females[9]


  • General
    • Caused by fungi (dermatophytes, non-dermatophyte molds, and yeasts)
    • Presents with discoloration of the nail, onycholysis, and nail plate thickening[10]
    • Toenails are affected seven to ten times more frequently than fingernails
    • Fingernail involvement usually implies toenail involvement unless immunocompromised


  • Dermatophytes (tinea unguium)
    • 90% of toenail, 75% of fingernail caused by Trichophyton mentagrophytes and Trichophyton rubrum[11]
    • Remaining dermatophytes: Epidermophyton floccosum, Microsporum species, Trichophyton verrucosum, Trichophyton tonsurans, Trichophyton violaceum, Trichophyton soundanense, Trichophyton krajdenii, Trichophyton equinum, and Arthroderma species[12]
  • Non-dermatophyte molds and yeasts
    • Causes include aspergillus species, Scopulariopsis species, Fusarium species, Acremonium species, Syncephalastrum species, Scytalidium species, Paecilomyces species, Neoscytalidium species, Chaetomium species, Onychocola species, and Alternaria species[13]
    • Account for approximately 10% of onychomycosis cases globally[14]
  • Yeast
    • Uncommon cause of onychomycosis
    • Candida albicans accounts for approximately 70% of onychomycosis caused by yeasts
    • Other: Candida tropicalis, Candida parapsilosi[15]
    • Increased risk: patients with chronic mucocutaneous candidiasis, immunodeficiency[16]


  • General
    • Direct contact of the nail with dermatophytes, non-dermatophyte molds, or yeasts.
    • Nail unit does not have effective cell-mediated immunity making it susceptible to fungal infection[17]
  • Fungal features
    • Keratin is degraded by production of enzymes that have proteolytic, keratinolytic, and lipolytic activity
    • This degradation compromises the barrier for invasion[18]
    • Fungal biofilms allows the fungi to evade current antifungal therapies and contribute to antifungal resistance[19]

Clinical Subtypes

  • Distal Lateral Subungual Onychomycosis
    • The most common clinical subtype
    • The fungal invasion begins at the hyponychium, then progresses to involve the distal nail bed and subsequently the nail plate
    • Fungus then migrates proximally through the nail plate, causing linear channels or "spikes"[20]
    • Etiology: Trichophyton rubrum, less commonly Trichophyton mentagrophytes
    • Presents as yellowish, whitish, or brownish discoloration of a distal corner of a nail[6]
  • White Superficial Onychomycosis
    • Upper surface of the nail plate is affected by the fungus, notably Trichophyton mentagrophytes
    • Presents as white dots or patches on the surface of the nail plate
    • The white dots and patches can be easily scraped off
  • Proximal Subungual Onychomycosis
    • Fungus invades the undersurface of the proximal nail fold in the vicinity of the cuticle and then extends distally
    • Etiology: Trichophyton rubrum, Fusarium spp.
    • Presents as an area of leukonychia in the proximal nail plate, moves distally with nail growth
    • Typically occurs in patients with immunodeficiency, especially Acquired Immunodeficiency Syndrome (AIDS)
  • Endonyx Onychomycosis
    • Fungal infection of the nail plate without infection of the nail bed
    • Etiology: Trichophyton soundanense, Trichophyton violaceum
    • Presents as milky patches of the nail plate, indentations, and lamellar splitting
  • Total Dystrophic Onychomycosis
    • Characterized by the total destruction of the entire nail apparatus
    • Can be thought of as end-stage of onychomycosis, may follow any of the other subtypes
    • Presents with a severely dystrophic and crumbed nail plate which is yellowish, diffusely thickened, and friable

Risk Factors

  • Foot/ Podiatric
  • Sports and Recreation
    • Participation in sports or fitness activities
    • Use of commercial swimming pools
    • Communal bathing
  • Systemic
  • Other
    • Living with family members with fungal infection
    • Poor health
    • Genetic factors
    • Tobacco Use

Differential Diagnosis

Differential Diagnosis Hand Pain

Differential Diagnosis Foot Pain

Clinical Features

  • History
    • Patients will report white, yellow or brown discoloration of the nail
    • Less commonly, green or black discoloration
    • Patients will often report deformities and cosmetic concerns
    • Toenails more common than fingernails, specifically the great toe
  • Physical Exam: Physical Exam Foot
    • The nail will often appear white or yellow-brown
    • Subungual Hyperkeratosis: thickening of the nail plate
    • Onycholysis: detachment of the nail from the nail bed
    • Onychauxis: thickening of the nail plate
    • Dermatophytoma: linear, single or multiple white, yellow, orange or brown bands on the nail plate[21]
      • Specific for onychomycosis
    • Tinea pedis is often present[22]



  • Strongly suspected based on clinical features
    • Nail discoloration
    • Subungual hyperkeratosis/debris
    • Onycholysis
    • Onychauxis
  • Clinical Diagnostic Accuracy[23]
    • Non-dermatologists: 66%
    • Dermatologists: 75%

Laboratory Testing

  • Potassium Hydroxide Prep
    • Can use KOH with direct microscopy to confirm diagnosis
    • Specificity: 38 to 78%[6]
    • Testing prior to initiating treatment is cost effective and recommended[2]
  • Histopathologic Examination
  • Periodic-Acid-Schiff (PAS) stain
    • Allows hyphae, pseudohyphae, spores, and yeasts to be visualized
    • Sensitivity: ranges from 82 to 88%, increases to 96% with fungal culture[24]
  • Fungal culture
    • Specific (83 to 100%) but not sensitive (60 to 65%)
    • Expensive, can take 2 to 4 weeks for results
  • Polymerase Chain Reaction (PCR) assays
    • Rapid and highly specific amplification of fungal DNA fragments
    • Quickly available (days), but expensive and not widely adopted[25]


  • See: clinical subtypes above



  • Indications
    • All
  • Confirmation of diagnosis
    • Consider confirming diagnosis prior to initiating therapy
    • Cost-effective and should be considered to avoid misdiagnosis
    • However, empiric treatment of onychomycosis is still performed by many physicians[26]
  • Oral Antifungals
    • Recommended for all types of onychomycosis, especially when ≥ 50% of the nail involved, multiple nails are infected, the nail matrix is involved, or dermatophytoma
    • Agents: include terbinafine (Lamisil), itraconazole (Sporanox, Sporaz, Orungal), and fluconazole (Diflucan, Celozole)
    • Terbinafine
      • 2017 Cochrane Review: Most effective of available therapy, should be considered first line therapy in most patients[27]
  • Topical Antifungals
    • Indications
      • Superficial onychomycosis
      • Early distal lateral subungual onychomycosis
    • Concurrent nail polish use should be avoided
    • Topical agents include efinaconazole (Jublia, Clenafin) (10% nail solution), tavaborole (Kerydin) (5% nail solution), ciclopirox (Ciclodan, Penlac, Loprox) (8% nail lacquer or hydrolacquer), amorolfine (Curanail, Loceryl, Locetar, Odenil) (5% nail lacquer), and terbinafine (Lamisil) (10% nail solution)
    • Topical therapy requires longer treatment courses (often 48 weeks or longer) and may be less effective than oral treatment
  • Laser Therapy
    • Help with cosmetic end points
    • However, not as effective as topical or oral antifungals[28]
    • Current role is not well delineated
  • Photodynamic Therapy
    • Two small studies involving 20 patients showed effectiveness in the treatment of onychomycosis[29][30]
    • Well-designed, large-scale, randomized studies are needed


  • Foot hygiene
    • Non-occlusive shoes
    • Keep feet dry and cold
    • Use absorbent socks
    • Clip nails short
  • Treat Tinea Pedis if present
  • Topical antifungal prophylaxis
    • Some authors suggest the use of topical antifungal therapy once weekly or twice monthly
    • Specifically in high-risk patients for up to two years after completion of treatment
  • Clean footwear
    • Ultraviolet C-based treatment device for footwear can be considered
    • Washing of running shoes (nonleather) in hot water.

Rehab and Return to Play


  • No clear rehab guidelines

Return to Play/ Work

  • Most athletes can continue to play

Complications and Prognosis


  • General
    • Good with appropriate treatment
  • Associated with poor response to therapy
    • Yellow streaks along the lateral margin of the nail
    • Presence of dermatophytoma
    • Onychomycosis caused by non-dermatophyte molds (in particular, Fusarium species)
    • Noncompliance
    • old age
    • Advanced disease
    • Nail matrix involvement
    • Subungual hyperkeratosis greater than 2 mm
    • Two feet-one hand syndrome
    • Immunodeficiency
  • Recurrences
    • Common with reported rates ranging from 10 to 53%[31]
    • Typically, recurrences occur within 3 years ofcompleting therapy
    • Recurrence may be caused by relapse or reinfection


  • If untreated
    • Cosmetic problems
    • Foot pain, discomfort
    • Physical impairment
    • Negatively impact quality of life
    • Interfere with standing, walking, nail function, and daily activities
    • Difficulty wearing shoes
    • Low self esteem
  • Reservoir fur cutaneous fungal infections[6]
  • Bacterial infections (immunocompromised, diabetics, etc)
  • Nail Deformities
    • Transverse over-curvature
    • Difficulties in trimming thick nail plates

See Also


  1. Thomas J, Peterson GM, Christenson JK, Kosari S, Baby KE. Antifungal drug use for onychomycosis. Am J Ther 2019; 26(3): e388-e96.
  2. 2.0 2.1 Gupta AK, Versteeg SG, Shear NH. Confirmatory testing prior to initiating onychomycosis therapy is cost-effective. J Cutan Med Surg 2018; 22(2): 129-41.
  3. Lipner SR, Scher RK. Onychomycosis: Clinical overview and diagnosis. J Am Acad Dermatol 2019; 80(4): 835-51.
  4. Sigurgeirsson B, Baran R. The prevalence of onychomycosis in the global population: A literature study. J Eur Acad Dermatol Venereol 2014; 28(11): 1480-91
  5. Gupta AK, Cernea M, Foley KA. Improving cure rates in onychomycosis. J Cutan Med Surg 2016; 20(6): 517-31.
  6. 6.0 6.1 6.2 6.3 Goldstein AO, Bhatia N. Onychomycosis: Epidemiology, clinical features, and diagnosis. In: Post TW, ed. Up To Date. Waltham, MA. (Accessed on June 30, 2019).
  7. Solís-Arias MP, García-Romero MT. Onychomycosis in children. A review. Int J Dermatol 2017; 56(2): 123-30.
  8. Cozzani E, Agnoletti AF, Speziari S, Schiavetti I, Zotti M, Persi A, et al. Epidemiological study of onychomycosis in older adults with onychodystrophy. Geriatr Gerontol Int 2016; 16(4): 486-91.
  9. Rosen T, Friedlander SF, Kircik L, Zirwas MJ, Stein Gold L, Bhatia N, et al. Onychomycosis: Epidemiology, diagnosis, and treatment in a changing landscape. J Drugs Dermatol 2015; 14(3): 223-33
  10. Hoy NY, Leung AK, Metelitsa AI, Adams S. New concepts in median nail dystrophy, onychomycosis, and hand, foot, and mouth disease nail pathology. ISRN Dermatol 2012; 2012: 680163.
  11. Gupta AK, Sibbald RG, Andriessen A, Belley R, Boroditsky A, Botros M, et al. Toenail onychomycosis - A Canadian approach with a new transungual treatment: Development of a clinical pathway. J Cutan Med Surg 2015; 19(5): 440-9.
  12. Fike JM, Kollipara R, Alkul S, Stetson CL. Case report of onychomycosis and tinea corporis due to Microsporum gypseum. J Cutan Med Surg 2018; 22(1): 94-6.
  13. Thomas J, Jacobson GA, Narkowicz CK, Peterson GM, Burnet H, Sharpe C. Toenail onychomycosis: An important global disease burden. J Clin Pharm Ther 2010; 35(5): 497-519.
  14. Welsh O, Vera-Cabrera L, Welsh E. Onychomycosis. Clin Dermatol 2010; 28(2): 151-9.
  15. Piraccini BM, Alessandrini A. Onychomycosis: A review. J Fungi (Basel) 2015; 1(1): 30-43.
  16. Piraccini BM, Alessandrini A. Onychomycosis: A review. J Fungi (Basel) 2015; 1(1): 30-43.
  17. Lipner SR, Scher RK. Onychomycosis: Clinical overview and diagnosis. J Am Acad Dermatol 2019; 80(4): 835-51.
  18. Zane LT, Chanda S, Coronado D, Del Rosso J. Antifungal agents for onychomycosis: New treatment strategies to improve safety. Dermatol Online J 2016; 22(3): 1.
  19. Gupta AK, Foley KA. Evidence for biofilms in onychomycosis. G Ital Dermatol Venereol 2019; 154(1): 50-5.
  20. Seebacher C, Brasch J, Abeck D, Cornely O, Effendy I, Ginter- Hanselmayer G, et al. Onychomycosis. J Dtsch Dermatol Ges 2007; 5(1): 61-6.
  21. Lipner SR, Scher RK. Onychomycosis: Clinical overview and diagnosis. J Am Acad Dermatol 2019; 80(4): 835-51.
  22. Piraccini BM, Alessandrini A. Onychomycosis: A review. J Fungi (Basel) 2015; 1(1): 30-43.
  23. Li DG, Cohen JM, Mikailov A, Williams RF, Laga AC, Mostaghimi A. Clinical diagnostic accuracy of onychomycosis: A multispecialty comparison study. Dermatol Res Pract 2018; 2018: 2630176.
  24. Westerberg DP, Voyack MJ. Onychomycosis: Current trends in diagnosis and treatment. Am Fam Physician 2013; 88(11): 762-70. PMID: 24364524
  25. Ghannoum M, Mukherjee P, Isham N, Markinson B, Rosso JD, Leal L. Examining the importance of laboratory and diagnostic testing when treating and diagnosing onychomycosis. Int J Dermatol 2018; 57(2): 131-8.
  26. Koshnick RL, Lilly KK, St Clair K, Finnegan MT, Warshaw EM. Use of diagnostic tests by dermatologists, podiatrists and family practitioners in the United States: Pilot data from a cross-sectional survey. Mycoses 2007; 50(6): 463-9.
  27. Kreijkamp-Kaspers S, Hawke K, Guo L, Kerin G, Bell-Syer SE, Magin P, et al. Oral antifungal medication for toenail onychomycosis. Cochrane Database Syst Rev 2017; 7: CD010031. PMID: 28707751
  28. Gupta AK, Versteeg SG. A critical review of improvement rates for laser therapy used to treat toenail onychomycosis. J Eur Acad Dermatol Venereol 2017; 31(7): 1111-8.
  29. Morgado LF, Trávolo ARF, Muehlmann LA, Narcizo PS, Nunes RB, Pereira PAG, et al. Photodynamic therapy treatment of onychomycosis with aluminium-phthalocyanine chloride nanoemulsions: A proof of concept clinical trial. J Photochem Photobiol B 2017; 173: 266-70.
  30. photodynamic therapy vs. intense pulsed light in the treatment of onychomycosis in the toenails. Photodermatol Photoimmunol Photomed 2019; 35(2): 69-77.
  31. Kemna ME, Elewski BE. A U.S. epidemiologic survey of superficial fungal diseases. J Am Acad Dermatol 1996; 35(4): 539-42.
Created by:
John Kiel on 23 February 2022 15:28:04
Last edited:
4 October 2022 12:44:41