Fungal Nail Infection (Onychomycosis)
Fungal nail infection, also known as onychomycosis or tinea unguium, is a fungal infection of the nail, most commonly caused by dermatophytes.
This updated UKMLA guide to fungal nail infection is based on NICE CKS, which covers causes, risk factors, symptoms, diagnosis, and management.
Causes
Most commonly caused by dermatophyte infections (85-90% cases)
- Most common: Trichophyton rubrum (~90%)
5-10% cases are caused by Candida species
- Most common: Candida albicans
- More commonly affects fingernails than toenails
Non-dermatophyte moulds such as Scopulariopsis, Scytalidium, Aspergillus, Fusarium, and Acremonium species are responsible for about 2–5% of cases of toenail onychomycosis (fingernails are rarely affected)
Risk Factors
| Non-modifiable factors |
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| Environmental factors |
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| Medical factors |
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Clinical Features
Fungal nail infection is often asymptomatic, especially in early stages. Patients may present because of nail discolouration, abnormal nail appearance, or cosmetic concern.
If symptomatic:
- Pain or discomfort, especially when wearing shoes or walking
- Difficulty cutting the affected nail
- Problems with footwear due to nail thickening or distortion
Typical nail changes include:
- Nail discolouration (white / grey / yellow / brown)
- Thickened nail plate
- Brittle / crumbly / distorted nail
- Subungual hyperkeratosis (thickened debris under the nail)
- Oncholysis (separation of the nail plate from the nail bed)
Fungal nail infection can present with different appearances depending on the site and pattern of infection:
| Onychomycosis subtype | Appearance / description |
|---|---|
| Superficial white | Small, flaky white patches and pits on the top of the nail plate
The nail becomes roughened and friable |
| Distal | The distal end of the nail is lifted up, and the free edge erodes
Linear channels / spikes may be seen when the infection spreads proximally |
| Lateral | White or yellow opaque streaks along one side of the nail |
| Proximal | White or yellow spots appear in the lunula (proximal growing end of the nail)
May cause onycholysis and white discolouration that spreads distally) |
| Subungual hyperkeratosis | Scaling under the distal nail, causing the nail to be discoloured, opaque, and thickened |
| Endonyx | White discolouration of the nail
In the absence of onycholysis and subungual hyperkeratosis |
| Total dystrophy | Marked thickening and hyperkeratosis – the nail plate is almost completely destroyed
Usually seen in immunocompromised patients and caused by Candida infection |
Onychomycosis may be associated with paronychia – where there is a painful red swelling at the periungual skin +/- pus collection (fluctuant mass)
Investigation and Diagnosis
If antifungal treatments are being considered → arrange nail clippings and/or scrapings for fungal microscopy and culture before starting treatment
Management
General Management / Self-Care Advice
Self-management:
- Keep nails trimmed short and filed down
- Wear well-fitting non-occlusive shoes, without high heels or narrow toes
- Wear cotton, absorbent socks
- Maintain good foot hygiene, including prompt treatment of any associated tinea pedis
- Wear protective footwear when using communal bathing places, locker rooms, and gymnasiums, to avoid re-exposure.
- Avoid prolonged or frequent exposure to warm, damp conditions if possible
- Avoid trauma to the nails if possible
Measures to prevent spread and transmission:
- Avoid sharing toenail clippers
- Replace old footwear that could be contaminated with fungal spores
Antifungal Treatment
Indications to Treat
DO NOT routinely offer antifungal treatment to all patients, only offer treatment if:
- Symptomatic (e.g. walking is uncomfortable), OR
- Significant psychological distress due to cosmetic appearance, OR
- Presence of comorbid conditions (e.g. diabetes, peripheral arterial disease, Raynaud’s phenomenon), OR
- Onychomycosis is the likely source of an associated fungal skin infection (e.g. tinea pedis)
If the infection is asymptomatic and the person is NOT bothered by its appearance → no treatment is necessary
Discuss with the patient their expectations for successful management of the condition before starting treatment. Onychomycosis is difficult to eradicate and often recurs.
Choice of Treatment
Before starting topical or oral antifungal treatment, confirm the diagnosis with nail clippings / scrapings for fungal microscopy and culture
| Scenario | Management |
|---|---|
| Very early, distal, and superficial nail involvement | Advise on the option of amorolfine 5% nail lacquer (topical antifungal)
Duration:
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| More extensive disease (not limited to very early, distal, or superficial nail involvement)
OR Self-care measures alone and/or topical treatment are not successful or appropriate |
Oral antifungal treatment
The choice depends on the identified organism:
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