Fungal Nail Infections

Synonyms: Onychomycosis(OM), tinea unguium.

Different fungal organisms may infect the nails, with different patterns of presentation, affecting any part of the nail from the nail bed, to the nail matrix and plate. The most common result is a poor cosmetic appearance of the affected nail(s), but the condition may also cause pain, disfigurement and functional impairment.

Whilst not life threatening, quality of life may be impaired through feelings of stigmatisation (comparable to other skin diseases)¹ and the avoidance of certain activities, e.g. swimming or other sports involving communal changing rooms.

This is one of the commonest dermatological conditions in the UK. Prevalence in the general population is thought to be between 3-5%,² although a recent European study suggested a Prevalence as high as 26.9%.³
The incidence of new cases of onychomycosis appears to be rising due to the increasing prevalence of diabetes in the population, more frequent incidence of immunosuppression and an ageing population.⁴

Risk factors

• Age – adults are ~30 times more likely than children to suffer the condition (affects 2.6% of children younger than 18 years, but as many as 90% of people older than 70 years).⁴
• Immunosuppression – illness or medications that suppress immune responses greatly increase the likelihood of suffering onychomycosis.
• Diabetes mellitus (OM affects up to 30% of diabetic patients)⁵ and peripheral vascular disease.
• Cutaneous fungal infection co-exists with onychomycosis in about 30% cases.⁴
• Living in a warm, humid climate.
• Participation in athletic/sporting activities, regular communal bathing and occlusive footwear.
• Prior trauma to the nail.

Dermatophytes

• Trichophyton rubrum or T. mentagrophytes cause over 90% of cases,⁶ with T. rubrum being responsible for about 70% of the total.⁴
• Other organisms in this group include Epidermophyton spp. and Microsporum spp.

Yeasts

Cause ~8% of total infections; particularly Candida albicans in the UK and Malassezia furfur in tropical climes.

Non-dermatophyte moulds

Cause about 2% of total infections, e.g. Scopulariopsis brevicaulis.

The toenails are affected in about 80% of cases of onychomycosis.⁶

Distal and lateral subungual onychomycosis (DLSO)

These form the vast majority of cases of onychomycosis:

• Nearly always caused by dermatophytes.
• Affect the hyponychium (epithelium of nail bed), often at the lateral edges initially.
• Spread proximally along nail bed causing creamy/buff discolouration, subungual hyperkeratosis and onycholysis.
• The nail plate is not affected initially but may become so in time.
• May be confined to one side of the nail or spread sideways to involve whole nail bed.
• Relentless progression until it reaches posterior nail fold.
• The nail plate becomes friable and may disintegrate, particularly after trauma.
• Surrounding skin is nearly always affected by tinea pedis.
• Fingernail DLSO has similar appearance although nail thickening is less common; toenail infection usually precedes it.

Superficial white onychomycosis (SWO)

This is less common than DLSO:

• Usually due to dermatophyte infection with T. mentagrophytes.
• Affects the surface of the nail plate rather than the nail bed.
• White rather than creamy discolouration.
• Notably flaky surface on the nail plate.
• Onycholysis is not usually a feature.
• Concurrent tinea pedis less common than in DLSO

Proximal subungual onychomycosis (PSO)

This is uncommon:

Most often found in the immunocompromised, e.g. HIV infection.
• May also affect diabetic/peripheral vascular disease patients.
• Usually due to dermatophyte infection.
• Tinea pedis usually co-exists.
• Leukonychia in the proximal nail fold, can extend to deeper layers of the nail.
• Nail plate becomes white proximally and remains normal distally.

Candidal onychomycosis

• Causes chronic paronychia with secondary nail dystrophy.
• May affect distal nail alone without paronychial involvement (usually in cases of Raynaud's phenomenon or peripheral vascular disease).
• Usually affects fingernails without toenail involvement in those whose occupations cause them to have constantly wet or allergen-irritated hands.
• Cuticular detachment and signs of infection and inflammation in the nail matrix may be observed.
• May complicate chronic mucocutaneous candidiasis or as a secondary infection due to other causes of nail disease, e.g. psoriasis.

Total dystrophic onychomycosis

• Represents a long-standing, severe, end-stage disease progressing from all of the above clinical patterns.
• Complete destruction of the nail plate is observed.

Only about 20-50% of discoloured or dystrophic-appearing nails have a fungal infection confirmed with dermatophyte on culture. Other causes include:

• Onychogryphosis (thickening and distortion of the nail, typically of the big toe, thought due to previous nail bed trauma)
• Trauma (tight shoes, nail biting)
• Poor foot care
• Eczema (irritant or allergic contact dermatitis)
• Lichen planus
• Subungual melanoma
• Psoriatic nail disease
• Bacterial paronychia, e.g. pseudomonas infection
• Systemic disease e.g. thyroid disease, diabetes, peripheral vascular disease
• Rare systemic disorders, e.g. Keratosis follicularis (Darier's disease), yellow nail syndrome, nail-patella syndrome, pachyonychia congenita
• Idiosyncratic drug reaction (especially tetracyclines, quinolones and psoralens)

• Nail material should be sent for microscopy. There is a high false negative rate (30-40%) and even positive results should be interpreted with caution as fungal organisms may exist as saprophytes, rather than as an invasive infection.
• Culture of nail material should also be undertaken as this increases sensitivity and will determine species but may take several weeks.
• Nail histology is not usually necessary unless there is reason to suspect another cause of nail pathology such as psoriasis.

• Diabetes mellitus
• Any cause of immunocompromise
• Raynaud's phenomenon
• Peripheral vascular disease
• Tinea pedis
• Occupational dermatitis of hands
• Chronic mucocutaneous candidiasis
• Psoriasis
• Nail trauma

To treat or not to treat?⁶

Traditionally there has been a reluctance to treat fungal nail infection as it has been seen as a trivial cosmetic problem.

• There is no medical necessity to treat and patients should be given the information to make an informed decision based on:
  • Even after successful treatment of the fungal infection, the nail may not look completely normal.
  • Treatment is only successful in up to 50% of people.
  • Even in those in whom it is successful, nails may appear abnormal for over 12 months due to their slow growth.
  • Relapse occurs in about 22% of people.²
  • Oral medication is taken for 6 weeks for fingernail infections and for 3 months for toenail infections.
  • Topical treatments may need to be applied for up to 12 months.
  • All medication has potential side-effects.
• However, anyone who presents should probably be offered treatment as the condition is likely to be causing significant distress if it has brought them to consult.
• If the condition progresses it can cause significant morbidity and functional disturbance, particularly in the elderly.
• There is also a public health argument for treating it, to lessen the reservoir of fungal spores in communal bathing areas, through reduction in the number of sufferers.

Cosmetic treatment

• Nail filing and nail polish can lessen cosmetic effects.
• A chiropodist may also be helpful.

Medical treatment

Topical therapy

In general, topical treatments are slightly better than placebo but often fail due to poor penetration of the nail plate.²

• They should be reserved for cases where there is an inability to tolerate systemic antifungals, or mild disease of the distal nail (affecting less than half the nail plate).⁶
• Treatment should be given daily for 6 months to 1 year.
• Can be used in cases of SWO or early-DLSO where infection is confined to the distal edge of the nail.
• 5% amorolfine is effective and appears to be the best topical agent in terms of its ability to penetrate the nail matrix.⁸
• 28% tioconazole is less effective but can be used successfully.⁹
• 8% ciclopirox is an effective treatment but does not currently have a UK licence.
• Combining topical ciclopirox with oral terbinafine appears to be more effective than oral terbinafine alone.¹⁰
• Topical nail patches containing anti-fungal agents such as sertaconazole show promising results and may be useful future therapies.¹¹

Systemic therapy⁶

Systemic treatment is recommended for most people as it is more effective.

1. Terbinafine:
   • Currently first-line with evidence of greater efficacy compared to itraconazole.
   • High cure rates and is usually effective after 3 months of therapy.
   • It is not licensed for use in children.
   • There have been cases of severe idiosyncratic skin and hepatotoxic reactions.
   • It interacts with rifampicin and cimetidine.
2. Itraconazole:
   • Highly active against Candida spp. but much less so against dermatophytes.
   • It can be given in a pulsed rather than continuous regimen (1 week on, 3 off). Cure rates are similar for both regimes.
   • It can cause hepatotoxicity and LFTs should be checked for treatment lasting longer than a month.
   • It is contraindicated in pregnancy and not licensed for use in children.
   • It interacts with a wide variety of commonly used pharmaceutical agents including warfarin, antihistamines, antipsychotics, digoxin, H2-antagonists, some statins and phenytoin.
3. Griseofulvin:
   • May be used in adults and children.
   • It is not expensive and there is a long experience of its use.
   • It requires long duration of treatment (at least 6 months) and has low cure and high relapse rates.
   • It interacts with warfarin, ciclosporin and the combined oral contraceptive pill (it is an hepatic enzyme inducer).
   • It is rarely used now although it is still used for trichophyton infections in children.
4. Fluconazole may be a useful systemic agent but is not currently licensed for this indication

• Side-effects of systemic anti-fungals include headache, itching, loss of sensation of taste, gastrointestinal symptoms, rash, fatigue and abnormal liver function.²
• One meta-analysis looking at safety of antifungals used to treat superficial fungal infections found a low incidence of adverse events in an immunocompetent population.¹² The risk of having asymptomatic serum transaminase elevation which did not require treatment discontinuation was less than 2.0% for all treatment regimens. The risk of an adverse liver reaction requiring treatment to be stopped ranged from 0.1% (continuous itraconazole) to 1.2% (continuous fluconazole).

Surgery

Nail avulsion, removal of nail plate, chemical treatments (e.g. 40–50% urea solution for very thickened nails) and matrixectomy may enhance the effectiveness of oral treatment.

Current UK guidelines⁶ advise against combining oral and topical treatments as there is insufficient evidence of benefit but others argue that using topical, systemic and/or surgical treatments in combination reduces costs and length of treatment.⁴

Refer where:⁷

• Diagnostic uncertainty remains.
• No response to medical treatment.
• Patient's choice to have surgical intervention.
• Children - rarer condition in children compared to adults and more limited treatment options.
• Suspected immune deficiency (e.g. mucocutaneous candidiasis).
• Extensive disease.
• Recurring candidal nail infections.

• Poor cosmetic appearance of hands/feet.
• Disfigurement and total destruction of nail plate.
• Paronychia.
• Damage to diabetic feet.
• Psychosocial problems due to embarrassment at cosmetic appearance.
• Pain and limitation of function, particularly in older patients.

• Cure rates vary from study to study but seem to be around 35–50% for those on terbinafine, which so far has been the most successful agent with best long-term results.
  

  There is often a discrepancy in clinical and microbiological cure rates in clinical trials.6,13Cure as defined by successful eradication of fungus on microscopy and culture will not always result in a normal appearance of the affected nail due to Delay of 6–12 months as the damaged nail grows out. The nail may have been dystrophic to begin with, predisposing it to fungal infection.

• Fingernail infections usually have much higher cure rates in the region of 70%.
• Untreated, fungal nail disease is usually progressive, leading to gradual destruction of the nail plate. However, there may be cases that spontaneously remit that do not present to their doctor.

Primary prevention is not practised, except where there is a cause of immunocompromise, such as AIDS, where prophylactic therapy may be considered.
Secondary prevention with topical terbinafine cream after cure with systemic terbinafine appears to be effective in reducing relapse rates.⁴

The following hygiene measures may help to limit spread and relapse:⁷

• Keep the area clean, dry well after bathing, change socks regularly.
• Avoid trauma to the nails.
• Do not share towels.
• Avoid repeated hand washing/ immersion of the hands in water if the fingernails are effected.
• Wear sandals or slippers in communal bathing places, locker rooms, gyms etc.