Onychomycosis

Onychomycosis, also known as, fungal nail infections affects toenails (more likely) or fingernails. Causing a yellow or white deformed and discoloured presentation. They are not serious in nature but treatment/ management can take time to heal the nail. Most common cause of the fungal infection is Trichophyton rubrum.

Epidemiology

About 10% of the global population has onychomycosis [1]
Males are more commonly affected by onychomycosis [2]
Reported mean prevalence in Europe and the US varies between 4.3-8.9% [3]
In the US point prevalence of fungal nail infection is estimated as 13.8% in adults [4]
Athletes are 2.5 times more likely to be affected by onychomycosis [5]
Fungal nail infections are more common in older people [6]

Pathophysiology of fungal nail infections [7]

Medical Student
- Fungal nail infections develop from triggering environments such as public places with bare feet exposure
- The environment caused by shoe wearing (dark, moist and warm) paired with the pressure placed on the nail unit breaks the hyponychial seal
- This allows entrance of the fungal organisms (dermophytes) into the nail bed
- This leads to dermatophytes growing on the keratin in the nails- spreading from the lesser toes, to the hyperkeratotic sole to the affected nail units.
- The nail is then affected firstly with a low-drage inflammation leading to its progression to a chronic stage infection
- The secondary damages infects the nail matrix, becoming hyperkeratotic and thickened in an attempt to fight the infection- thus leading to the distortion and detaching of the nail over time.
Patients
- Fungal nail infections develop from triggering environments such as public places with bare feet exposure
- The environment caused by shoe wearing (dark, moist and warm) paired with the pressure placed on the nail unit breaks the hyponychial (thick layer of skin under the free nail) closing
- This allows entrance of the fungal organisms into the nail bed
- This leads to the organisms growing on the keratin (substance used to grow nails, hair and skin) in the nails- spreading from the lesser toes, to the hyperkeratotic (high levels of keratin) sole of the foot to the affected nail units (the nail plate and soft tissue surrounding it)
- The nail is then affected firstly with a low- stage inflammation leading to its progression to a chronic (long term) stage infection
- The secondary damages infects the nail matrix (where the fingernail and toenails start to grow), becoming hyperkeratotic and thickened in an attempt to fight the infection- leading to a change in shape of the nail as well as detachment of the nail over time.

Source: DermNetNZ.org

Onychomycosis
Extensive nail damage with yellow/white debris

Source: DermNetNZ.org

Onychomycosis
Infected toe nails of the distal (furthest from middle) and lateral (away from the middle) regions

Causes [8]

Warm, dark and moist environments contribute to fungal growth on the nail
Not keeping feet clean and dry
Walking in spaces with a high risk of spreading infections

Risk factors
- History of athlete’s foot (tinea pedis)
- History of nail dystrophy (wasting of tissues or defective nutrition to the nail)
- Older age
- Male
- Exposure to spaces/ people with athletes feet or fungal nail infections
- Diabetes
- Peripheral vascular disease- reduced circulation of blood to areas of the body
- Weakened immune system
- Psoriasis
- Damaged nails [1,8]
Presentations
- Thickened nail
- White, chalky colour discolouration
- Yellow, black or green discolouration of the nail [1]
- Fragile nails
- Cracking in the nails
- Separation of the nail from the nail bed (onycholysis) [9]
- Pain or discomfort
- Brittle nails (pieces may break off) [8]

Source: DermNetNZ.org

Onychomycosis
Total fingernail involvement on type 6 skin (Fitzpatrick scale)

Source: VisualDx and Skinsight

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Investigations

Clinical assessment of appearance
Microscopic examination of sample- to rule out different diagnosis such as psoriasis.
Culture of scrapings- to find the organism that is causing the fungal infection
Polymerase chain reaction of clippings- using the distal (furthest point from the toe) part of the toe/ finger nail is preferred
Histopathologic (using cells) examination with an acid-Schiff (PAS) stain- examination of nail clippings with a PAS stain can confirm the diagnosis [1,9]

Differential diagnosis [10]
- Psoriasis- nail deformation and pitting
- Lichen planus- condition that affects the skin and nails, can become thin and discoloured
- Eczema- nails are irregular and thickened
- Alopecia areata- brittle nails
- Bacterial infections- nail discolouration to black and green
- Viral warts- distorted nail growth
- Onychogryphosis- thickened nails
- Trauma- nail seperates from nail bed
- Yelow nail syndrome- nail discolouration
- Melanoma of the nail (subungual)- discolouration to black and nail distortion

Source: Mind The Gap

Onychomycosis
Extensive nail involvement with purple debris

Source: DermNetNZ.org

Onychomycosis
White discolouration of the distal (furthest from middle) nail

Management [1]

Medical Student
- Many cases present with mild or asymptomatic, meaning they are unlikely to cause complications
- Lifestyle advise such as;
  - Cutting nails
  - Drying feet properly after bathing
  - Wearing absorbent socks
  - Using antifungal powder
  - Considering not using old shoes- can pose as a triggering environment for fungal growth
- The usages of drug treatment can be proposed for cases such as;
  - History of ipsilateral cellulitis
  - Diabetes
  - Presense of symptoms that impact quality of life
  - Mental impact caused by the infection
  - Desire for appearence improvement
- These drugs include;
  - Oral Terbinafine
  - Oral Itraconazole
- This will not necessarily be carried out until the nail is completely fixed as the nature of the drugs attach to the nail bed- remaining effective post ceasure of the oral administation.
- Newer medications such as can be used;
  - Efinaconazole
  - Tavaborole
- These can penerate the nail plate and have been found to be more effective as a form of treatment.
Patients
- Many cases present with mild or no symptoms, meaning they are unlikely to cause complications
- Lifestyle advise such as;
  - Cutting nails
  - Drying feet properly after bathing
  - Wearing absorbent socks
  - Using antifungal powder
  - Considering not using old shoes- can pose as a triggering environment for fungal growth
- The usages of drug treatment can be proposed for cases such as;
  - History of ipsilateral (same side of the body) cellulitis
  - Diabetes
  - Presense of symptoms that impact quality of life
  - Mental impact caused by the infection
  - Desire for appearence improvement
- These anti-fungal drugs include;
  - Oral Terbinafine
  - Oral Itraconazole
  - This will not necessarily be carried out until the nail is completely fixed as the nature of the drugs attach to the nail bed- remaining effective after stopping the period of oral administation
- Newer medications such as can be used;
  - Efinaconazole
  - Tavaborole
    - These can enter the nail plate and have been found to be more effective as a form of treatment.

Complications [10]
- Distress to mental health and self esteem
- Difficulty walking, exercising or wearing shoes
- Bacterial infections
- Cellulitis (inflammation of skin)
- Injury to the surrounding skin caused by nail changes
- Mass growing keratin (protein that creates nails and hair) below the nail plate (dermatophytoma)
- Contagious source if living with others

Source: DermNetNZ.org

Onychomycosis
Infection of several nails

Source: DermNetNZ.org

Onychomycosis
The fungus, candida, affecting the nail causing white/yellow discolouration

Myths behind fungal nail infections
- Fungal nail infections are always minor
- Nail polish will prevent fungal infections
- Soaking your feet in bleach will cure fungal infections
- Poor hygiene causes fungal infections [11]
- Fungal infections can be cured by removing the nail
- Fungal nail infections can be cured quickly [12]

Questions you may want to ask your doctor
- How can I treat discomfort from the infection?
- Can it spread to others? How can I prevent that from happening?
- How long will it take for treatment to work?
- What can I do if the infection is impacting my self esteem?
- How do I avoid getting an infection again in shared spaces?
Support
- American Academy of Dermatology
- Centres for Disease Control and Prevention
- Canesten.co.uk