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Key sources
The following summarized guidelines for the evaluation and management of onychomycosis are prepared by our editorial team based on guidelines from the German-Speaking Mycological Society (DMykG/DDG/BVDD/APD/DGKJ/DGHM/DGPI 2023), the Japanese Dermatological Association (JDA 2020), the British Association of Dermatologists (BAD 2014), and the American Academy of Family Physicians (AAFP 2014).


1.Screening and diagnosis

Diagnosis: confirm the diagnosis of onychomycosis with a test, such as potassium hydroxide preparation, culture, or periodic acid-Schiff stain, before initiating treatment.
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2.Diagnostic investigations

History and physical examination
Elicit history, including underlying diseases (diabetes, circulatory disorders), disease course, risk factors (sports participation), and other disease cases in the surroundings.
Obtain integumentary assessment, especially to inspect the type of involvement and to assess for other clinical manifestations of dermatophytosis, such as tinea unguium in the fingernails, tinea pedum, and additional tinea corporis.

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  • Direct microscopy

  • Fungal culture

  • Molecular testing

  • Resistance testing

3.Diagnostic procedures

Histological examination
Obtain histological examination in patients with suspected fungal infection not confirmed by other methods or when such methods are not available.
Consider obtaining histological examination in combination with fungal staining (periodic acid-Shiff) or Grocott-Gomori staining in previously treated patients with negative mycological test results. Combine potassium hydroxide preparation and histology to increase diagnostic sensitivity.

4.Medical management

General principles
Take into consideration the following factors when deciding between topical and combined topical-systemic antifungal treatment:
involvement of the nail matrix
number of affected toenails or fingernails
extent of the surface affected per nail
patient multimorbidity
drug interactions
expected compliance
Define the following goals in the treatment of onychomycosis:
complete elimination of the pathogen as quickly and safely as possible, defined by negative repeat test (PCR method if possible)
largely healthy nails clinically (defined usually as < 5-10% residual change at the distal nail margin)
prevention of further spread and/or interruption of infection chains

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  • Systemic antifungals

  • Topical antifungals

5.Therapeutic procedures

Atraumatic nail removal
Perform atraumatic nail removal to reduce the fungally infected and hyperkeratotic nail material as an adjuvant measure before topical and systemic antifungal treatment in patients with onychomycosis.
Consider combining atraumatic nail removal with systemic antifungal treatment.

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  • Laser and photodynamic therapies

6.Surgical interventions

Surgical nail removal: as per DDG 2023 guidelines, do not perform traumatic (surgical) nail extraction in patients with onychomycosis.

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  • Nail debridement

  • Nail drilling

7.Specific circumstances

Pediatric patients: offer terbinafine (62.5 mg/day for < 20 kg weight, 125 mg/day for 20-40 kg weight, 250 mg/day for > 40 kg weight; for 6 weeks for fingernail infection and 12 weeks for toenail infection) as first-line therapy in pediatric (aged 1-12 years) patients with dermatophyte onychomycosis. Obtain baseline liver function tests and CBC.
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8.Preventative measures

Antifungal prophylaxis: consider offering long-term antifungal prophylaxis with amorolfine- or ciclopirox-containing nail lacquer preparations (applied less frequently than for treatment) after successful onychomycosis treatment.

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  • Footwear disinfection

9.Follow-up and surveillance

Follow-up: assess for clinical healing and obtain mycological testing to monitor treatment.
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