II. Definitions

  1. Onychomycosis
    1. Fungal infection affecting the Toenail or Fingernail

III. Epidemiology

  1. Prevalence
    1. General population: 10% Prevalence (worldwide)
    2. Age under 20 years: 3% Prevalence (U.S.)
    3. Age over 60 years: 28% Prevalence (U.S.)
  2. Most common Nail Disorder (accounts for 50% of Nail Disorders)
  3. Rarely occurs in children unless predisposing factors
    1. Immunosuppression (e.g. AIDS)
    2. Extensive fungal skin involvement
    3. Family History of Onychomycosis

IV. Pathophysiology

  1. Person to person transmission
  2. Toenails are more commonly affected than Fingernails
    1. Decreased blood supply and slower growth (compared with Fingernails)
    2. Dark, moist environment

V. Risk Factors

  1. Older age (especially over age 60-70 years)
  2. Tinea Pedis or other fungal infection
  3. Swimming pools, locker rooms or other use of shared bathing areas
  4. Psoriasis
  5. Nail deformity or Trauma
  6. Hyperhidrosis
  7. Tobacco Abuse
  8. Immunodeficiency
    1. Diabetes Mellitus (>1.9 fold increased risk)
    2. HIV Infection (15-40% Prevalence)

VI. Types

  1. Distal Subungual (most common)
    1. Affects distal and lateral Toenails and Fingernails
    2. Starts distally (at Hyponychium) and spreads into nail plate and nail bed
    3. Associated with hyperkeratosis with secondary Onycholysis and ultimately Dystrophic Nails with yellow or brown discoloration
    4. Acquired through break in skin at nail undersurface (e.g. seocndary to Tinea Pedis, Paronychia)
    5. Most common etiology: Trichophyton rubrum
      1. However any of the fungal organisms may be causative
  2. Superficial or superficial white Onychomycosis (10% of cases)
    1. Most common etiology: Trichophyton mentagrophytes
    2. Typically white (but sometimes black) powdery patches forming horizontal nail lines
  3. Endonyx Subungual (rare subtype of distal subungual)
    1. Etiologies
      1. Trichophyton soudanense
      2. Trichophyton violaceum
    2. Direct infection of full nail thickness without affecting nail bed
    3. May affect entire Toenails
      1. Starts as opaque, well demarcated milky-white spots
      2. Spots coalesce to involve entire nail
    4. Associated findings
      1. Lamellar splitting and nail indentations
      2. No hyperkeratosis or Onycholysis
  4. Proximal Subungual (least common)
    1. Most common etiology: Trichophyton rubrum
    2. Affects proximal Fingernails and Toenails
    3. Fungi invade proximal nail fold to enter nail
    4. Hyperkeratosis and debris form under proximal nail resulting in Onycholysis that spreads gradually from proximal to distal nail
    5. Predisposing factors
      1. Immunocompromised status (e.g. HIV Infection or AIDS)
      2. Local Trauma may also result in similar presentation
  5. Candida Onychomycosis (rare)
    1. Associated with Chronic Paronychia (Candida)
    2. More common in Immunocompromised state
  6. Total dystrophic Onychomycosis
    1. Total nail plate destruction from above types (especially distal subungual)
    2. Associated with long-term infection that thickens the nail and ultimately destroys the nail structure

VII. Signs: Nail plate changes

  1. Discoloration (white or yellow)
  2. Opacification
  3. Distribution based on type (see above)

VIII. Technique: Obtaining Nail specimens

  1. Nail preparation
    1. Wipe the nail with 70% Isopropyl Alcohol
    2. Use sterile nail clipper to obtain 8-10 nail shards if possible (improves Test Sensitivity)
    3. Obtain subungual material with 2 mm curette or #15 blade
    4. Nail drill may be used for proximal nail location
  2. Techniques for specific nail types
    1. Distal subungual Onychomycosis
      1. Clip nail short
      2. Apply curette to nail bed near cuticle for sample
      3. Also scrape underside of nail plate
    2. White superficial Onychomycosis
      1. Scrape nail plate surface white area for sample
    3. Proximal superficial Onychomycosis
      1. Pare nail plate near lunula
      2. Curette sample from infected nail bed
    4. Candidal Onychomycosis

IX. Labs: Miscellaneous

  1. Potassium Hydroxide (10-20% KOH): Subungual debris scraping
    1. Test Sensitivity: 48%
    2. Test Specificity: 72%
  2. Periodic acid-Schiff Stain (PAS Stain)
    1. Test Sensitivity: 82%
  3. Nail Fungal Culture
    1. Test Sensitivity: 53%
    2. Test Specificity: 82%
  4. Nail Biopsy: Periodic acid schiff stain (effective, but expensive and not widely available)
    1. Test Sensitivity: 92%
    2. Test Specificity: 72%
  5. Fungal PCR
    1. Results in 3 days where available
    2. Expensive and not widely available
  6. References
    1. Wilsmann-Theis (2011) J Eur Acad Dermatol Venereol 25(2): 235-7 [PubMed]

X. Differential Diagnosis

  1. See Dystrophic Nail
    1. Only 50% of Dystrophic Nails are Onychomycosis
  2. Infection
    1. Candida Paronychia (Chronic Paronychia)
    2. Bacterial Paronychia (Acute Paronychia)
    3. Periungual wart
    4. Herpetic Whitlow (Herpes Simplex Virus)
  3. Trauma
    1. Ingrown Toenail
    2. Local nail Trauma (e.g. tight footwear, manicures or pedicures)
  4. Skin conditions
    1. Psoriasis
    2. Lichen Planus (especially Fingernails)
      1. Variant: Twenty-Nail Dystrophy (children)
    3. Contact Dermatitis
  5. Nail bed tumor
    1. Fibroma or Dermatofibroma (benign)
    2. Subungual Melanoma
    3. Bowen Disease (Squamous Cell Carcinoma)
  6. Miscellaneous causes
    1. Yellow Nail Syndrome
  7. References
    1. Allevato (2010) Clin Dermatol 28(2): 164-77 [PubMed]

XI. Management: General Measures

  1. Keep feet dry
    1. Wear cotton socks and change 2-3 times per day
    2. Wear shoes that are breathable
  2. Reduce fungus exposure
    1. Wear foot protection in shared showers (locker room)
    2. Treat Tinea Pedis
  3. Consider nail removal in severe Onycholysis
  4. Optimize chronic disease management
    1. Diabetes Mellitus
    2. Tobacco Cessation
  5. Cosmetic procedures
    1. Laser Therapy (e.g. PinPointe)
      1. Treats only the cosmetic appearance of the nail (not the fungal infection)
  6. Antifungal Medications
    1. Consider Topical Antifungal to treat periungual fungus as adjunct to those below
    2. Consider longer Antifungal course in some patients
      1. Slow Nail Growth
      2. Extensive nail plate involvement
      3. Diminished blood supply
        1. Peripheral Vascular Disease
        2. Diabetes Mellitus

XII. Management: Antifungal agents

  1. Indications
    1. Immunocompromised patients
    2. Secondary infection risk (e.g. Diabetes Mellitus)
    3. Foot Pain
    4. Cosmesis (warn regarding imperfect cure rates, and nails may remain dystrophic)
  2. Background
    1. Confirm Onychomycosis and not a mimic on differential diagnosis
      1. Onychomycosis is visually misdiagnosed in up to 50% of patients with Dystrophic Nails
    2. Cure rates are listed in clinical cure (appearance) and mycologic cure (culture/microscopy)
    3. Monitoring of liver transaminases is typically baseline and at 4-6 weeks after starting therapy
  3. Terbinafine (Lamisil)
    1. Indications
      1. First-line therapy due to best efficacy and low cost ($4 per month)
    2. No further Liver Function Tests needed if baseline Liver Function Tests are normal and no systemic symptoms
    3. Dosing: Daily
      1. See Terbinafine for dosing and lab monitoring
      2. Child 10 to 20 kg: 62.5 mg once daily
      3. Child 20 to 40 kg: 125 mg once daily
      4. Adult (and child >40 kg): 250 mg once daily
    4. Dosing: Pulsed
      1. Take for 4 weeks on, then 4 weeks off, then 4 weeks on
      2. Yadav (2015) Indian J Dermatol Venereol Leprol 81(4):363-9 [PubMed]
    5. Duration
      1. Fingernails: 6 weeks
      2. Toenails: 12 weeks
    6. Most effective oral Antifungal agent for treatment of Onychomycosis
    7. Cure rate
      1. Clinical cure: 66%
      2. Mycologic cure: 76% with negative culture/microscopy
  4. Itraconazole (Sporanox)
    1. Indications
      1. Onychomycosis due to yeast or non-dermatophytes
    2. See Itraconazole for dosing and lab monitoring
    3. Fingernails
      1. Daily (continuous): 200 mg daily for 6 weeks
      2. Monthly (pulsed): 200 mg twice daily for one week/month for 2-3 months
    4. Toenails
      1. Daily (continuous): 200 mg daily for 12 weeks
      2. Monthly (pulsed): 200 mg twice daily for one week/month for 3-4 months
    5. Cure rate
      1. Clinical cure: 70%
      2. Mycologic cure: 69% with negative culture/microscopy (63% if pulse dosing)
  5. References
    1. De Doncker (1996) Arch Dermatol 132:34-41 [PubMed]
    2. Evans (1999) BMJ 318:1031-5 [PubMed]
    3. Faergernann (1995) J Am Acad Dermatol 32: 750-3 [PubMed]
    4. Gupta (2004) Br J Dermatol 150(3): 537-44 [PubMed]

XIII. Management: Refractory cases

  1. Nd:YAG Laser (Neodymium:yttrium-aluminum-garnet laser)
    1. Efficacy based only on small studies
    2. 61% complete mycologic cure rates after 1-3 treatments at 4-6 week intervals
    3. Kimura (2012) J Drugs Dermatol 11(4): 496-504 [PubMed]

XIV. Management: Less effective agents (generally avoid these for Onychomycosis)

  1. Background
    1. Avoid systemic agents listed here (Griseofulvin and Fluconazole) for Onychomycosis
      1. Agents listed above (Terbinafine and Itraconazole) have better efficicacy
      2. Griseofulvin has greater toxicity risk
    2. Avoid topical agents in Onychomycosis
      1. Minimally if at all effective in Onychomycosis
      2. Local irritation is common
      3. If a topical agent is used, Ciclopirox (Penlac) would be preferred in combination with Debridement
  2. Fluconazole (Diflucan)
    1. See Fluconazole for dosing and lab monitoring
    2. Dosing
      1. Child: 3-6 mg/kg (up to 150 to 300 mg) once weekly
      2. Adult: 150 to 300 mg once weekly
    3. Cure rate
      1. Clinical cure: 41%
      2. Mycologic cure: 48% with negative culture/microscopy
    4. References
      1. Gupta (2004) Br J Dermatol 150(3): 537-44 [PubMed]
      2. Scher (1998) J Am Acad Dermatol 38:S77-S86 [PubMed]
  3. Griseofulvin
    1. Low cure rates (30-45%) even when taken for up to 6-12 months at 500-1000 mg daily
    2. Faergernann (1995) J Am Acad Dermatol 32: 750-3 [PubMed]
  4. Ciclopirox (Penlac) 8% nail lacquer
    1. Requires 48 week application
    2. Generic Ciclopirox costs $300 per year to treat two nails in 2020
    3. Marginally better than Placebo with 7% clinical cure rate (up to 36% with negative culture/microscopy)
      1. When used with Debridement may offer up to 77% mycotic cure rate (negative culture/microscopy)
    4. References
      1. Gupta (2000) J Am Acad Dermatol 43(4 suppl) S70-80 [PubMed]
      2. Malay (2009) J Foot Ankle Surg 48(3): 294-308 [PubMed]
  5. Efinaconazole (Jublia) 10% nail lacquer
    1. Topical agent for Onychomycosis that appears more effective than Penlac, but less effective than oral agents
    2. Apply 2 drops daily to a great toe nail (or 1 drop for other nails)
    3. Very expensive ($450 for 4 ml - treats one great Toenail per 6 weeks) and may cost $9000 for a year course
    4. Clearance rates<20% per year
    5. (2014) Presc Lett 21(8): 47
  6. Tavaborole (Kerydin)
    1. Similarly very expensive Topical Antifungal with low efficacy
  7. Argentina pichinchensis (snakeroot extract)
    1. Similar efficacy to Ciclopirox (Penlac)
    2. Romero-Cerecero (2008) Planta Med 74(12): 1430-35 [PubMed]
  8. Dual-wavelength near-infrared laser (Noveon)
    1. Marginal benefits by study with atypical measures of clinical cure and 30% mycologic cure
    2. Landsman (2010) J Am Podiatr Med Assoc 100(3):166-77 [PubMed]
  9. OTC Nail Lacquers (e.g. Fungi-Nail)
    1. Over-the-counter (otc) Antifungal agents that treat periungual fungus, but do not penetrate the nail to treat Onychomycosis
  10. Vicks VapoRub
    1. No proven efficacy in Onychomycosis
  11. Tea Tree Oil
    1. No proven efficacy in Onychomycosis

XV. Prognosis

  1. Recurrence rate after treatment: 20-50%

XVI. Complications

  1. Cellulitis in older patients
  2. Diabetic Foot Ulcer

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Related Studies

Ontology: Onychomycosis (C0040261)

Definition (MSH) A fungal infection of the nail, usually caused by DERMATOPHYTES; YEASTS; or nondermatophyte MOLDS.
Definition (NCI) Fungal infection of a fingernail or toenail.
Concepts Disease or Syndrome (T047)
MSH D014009
ICD9 110.1
ICD10 B35.1
SnomedCT 186988000, 30757001, 266149008, 266215006, 154397004, 414941008, 402134005
English Onychomycoses, ONYCHOMYCOSIS, OM - Onychomycosis, Fungus, Nail, Nail Fungus, Nail tinea, dermatophytosis of nail, fungal infection of nail, dermatophytosis of nail (diagnosis), fungal infection of nail (diagnosis), Nail fungal infection NOS, Ringworm of nails, Dermatophytic onychia, Onychomycosis [Disease/Finding], nail tinea, Infection;fungus;nail(s), onychomycoses, dermatophytic onychia, fungal nail infection, Onychomycosis, Fungal nail infection, Tinea of nail - onychomycosis, (Nail: [dermatophytosis] or [fungal infection]) or (onychomycosis) or (tinea unguium) (disorder), Tinea unguium (disorder), (Nail: [dermatophytosis] or [fungal infection]) or (onychomycosis) or (tinea unguium), Onychomycosis (& [tinea of nail]) (disorder), Onychomycosis (& [tinea of nail]), Dermatophytosis of nail (disorder), Fungal infection of claw, Tinea Unguium, Onychomycosis due to dermatophyte (disorder), Onychomycosis due to dermatophyte, onychomycosis, dermatophytic; onychia, dermatophytosis; nail, fungus; infection, nail, infection; fungus, nail, nail; dermatophytosis, nail; ringworm, onychia; dermatophytic, ringworm; nail, tinea; unguium, unguium; tinea, Fungal infection of nail, NOS, Dermatophytosis of nail, Tinea unguium, Fungal infection of nail, Tinea of nail, Onychomycosis (disorder), Ringworm of nail, tinea unguium
French ONYCHOMYCOSE, Infection fongique de l'ongle, Onyxis fongique SAI, Onyxis dermatophytique, Teigne de l'ongle, Dermatophytose unguéale, Tinea unguium, Onychomicose, Dermatophytose de l'ongle, Onychomycose, Mycose de l'ongle, Mycose unguéale
Portuguese ONICOMICOSE, Infecção micótica da unha, Onicomicose NE, Fungo de Unha, Tinha das unhas, Dermatofitose ungueal, Tinha da unha, Micose de Unha, Fungo de Unhas, Micoses Ungueais, Micose Ungueal, Onicomicose
German ONYCHOMYKOSE, Pilzinfektion der Naegel NNB, Pilzinfektion des Nagels, Ringwurm der Naegel, Dermatophytose der Naegel, Tinea der Naegel, Tinea unguium, Nagelmykose, Nagelpilz, Onychomykose
Dutch nagelschimmelinfectie NAO, schimmelinfectie van de nagel, dermatofytose van nagel, tinea unguium, nageltinea, ringworm op nagels, dermatofytisch; onychia, dermatofytose; nagel, fungus; infectie, nagel, infectie; fungus, nagel, nagel; dermatofytose, nagel; ringworm, onychia; dermatofytisch, ringworm; nagel, tinea; unguium, unguium; tinea, onychomycose, Mycose, onycho-, Onychomycose, Tinea unguium
Italian Infezione micotica dell'unghia, Infezione micotica ungueale NAS, Tigna ungueale, Dermatofitosi dell'unghia, Tigna dell'unghia, Tinea Unguium, Tinea delle unghie, Onicomicosi
Spanish Infección de la uña por hongos, Infección ungueal por hongos NEOM, Hongo de Uña, onicomicosis debido a dermatofito, onicomicosis debido a dermatofito (trastorno), Tiña ungueal, Tiña de las uñas, Dermatofitosis de uña, oniquia dermatofítica, infección fúngica de la uña, tiña ungular, tiña de las uñas, dermatofitosis ungueal (trastorno), Micosis de Uña, Micosis Ungueal, Hongo de Uñas, Micosis Ungueales, tiña de uña, dermatofitosis ungueal, onicomicosis (trastorno), onicomicosis, infección micótica de la uña, onicomicosis por dermatofito (trastorno), onicomicosis por dermatofito, tiña ungueal, Onicomicosis
Japanese 爪部真菌感染, 爪真菌感染NOS, ソウブシンキンカンセン, ツメシンキンカンセンNOS, ソウシンキンカンセンNOS, ツメシンキンショウ, 爪の皮膚糸状菌症, ツメノヒフシジョウキンショウ, ツメハクセン, ソウハクセン, 爪甲真菌症, 爪真菌症, 爪白癬, 白癬-爪, 爪真菌症(ツメシンキンショウ)
Swedish Nagelsvamp
Czech tinea unguium, onychomykóza, Mykotická infekce nehtu NOS, Mykotická infekce nehtu, Onychomykóza, Dermatofytóza nehtu, Plísňové onemocnění nehtu
Finnish Kynsisilsa
Korean 손발톱 백선증
Polish Grzybica paznokci
Hungarian köröm dermatophytosisa, Köröm gombás fertőzése, Köröm gombás fertőzése k.m.n., Köröm bőrgombája, Tinea unguium, Onychomycosis, köröm tinea
Norwegian Neglesopp, Onykomykose, Tinea unguium, Dermatofytisk onyki, Negleringorm