What is a fungal nail infection?
A fungal infection of the nail, also known as onychomycosis or tinea Unguium, .is a disease of the keratin layer under the nail. These infections can be difficult to treat and affect approximately 3% of the population in the UK. Fungal Nail Infections are rare in children, but the incidence increases with age. If you are aged over 60, there is a one in five chance you will have a nail infection and if you have diabetes, this increases to a one in three chance. The toenails are most commonly affected, although you may also get infections in the fingernails. Untreated fungal nail infection causes the nail to become thickened, weakened and prone to fragmentation. They may also discolour and become brown or yellow. It is important that treatment is sought as early as possible, as nail infections are much easier to treat in their early stages. In some individuals, a nail infection can lead to more serious complications, especially if there are associated medical conditions or poor circulation. These infections are not merely cosmetic and can spread to other nails if left untreated. Over 90% of skin and fungal nail infections in man are due to fungi known as dermatophytes, i.e. filamentous fungi.
Some other nail conditions can look quite similar to nail infections. These include psoriasis of the nails, nail damage and changes caused by ageing through poor arterial circulation in the lower limbs.
How common are nail infections?
In the UK, the incidence of fungal nail infections is considered to be about 3% of the general population. The risk of getting a fungal nail infection increases with age. The typical fungal nail infection patient is a middle-aged or older man or woman. In children fungal nail infection is very rare. Some medical conditions can make a person more prone to contracting a nail infection, such as diabetes.
Fungal nail infections are also common amongst those persons practising sports, especially where they are using public changing rooms. Fungal spores can be passed onto the changing room floor and picked up by unsuspecting individuals, so nails should be checked frequently for any changes or discolouring.
Incidence in the UK:
| Amongst the General Population | 3% |
| Amongst those with Diabetes | 35% |
| Amongst those aged over 60 | 20% |
| Amongst those aged over 70 | 50% |
What type of fungus causes fungal nail infections?
In western countries the vast majority (over 90%) of fungal nail infections are caused by Trichophyton, Microsporum and Epidermophyton dermatophyte fungi. The most common species are Trichophyton rubrum, Trichophyton mentagrophytes and Trichophyton tonsurans. Bad foot hygiene may predispose a person to these infections. Other fungi able to cause nail infections are some types of mould and yeasts of which Candida albicans, is the most common.
What types of fungal nail infections are there?
Fungal nail infections are classified according to the site of the infection and the causal pathogen. All fungal nail infections can ultimately lead to complete destruction of the nail plate, hence the need to treat the infection as soon as possible.
- A fungal infection beginning at the tip or side of the nail which spreads gradually towards the base of the nail. This is known as DLSO (Distal Lateral Subungual Onychomycosis). This is the most common type of nail infection and is caused by a fungal spore getting underneath the front edge of the nail or down the side of the nail. The nail will often appear opaque, yellow or brown in colour. If left untreated this infection will spread down the nail and infect the nail matrix, making treatment much more difficult.
- Another variation of the above is WSO (White Subungual Onychomycosis). This appears as a white clouding of the nail which may be caused by the dermatophyte Trichophyton mentagrophytes. A superficial fungal nail infection is rarer than those infections beginning at the tip or side of the nail. Again the site of infection is under the front edge of the nail or down the side of the nail.
- Endonyx Onychomycosis is a rare form of nail infection which is caused by a pathogen penetrating the surface of the nail plate itself. This has as a white, patchy appearance and can be quite tough to treat.
- Those fungal nail infections beginning at the base of the nail are the rarest and also the most difficult to treat. This is known as PSO (Proximal Subungual Onychomycosis). This are often associated with poor arterial blood circulation to the lower limb, diabetes or weakening of the body’s immune defences, e.g. due to immune suppression by medicines or a disease. A fungal infection beginning at the base of the nail thickens, weakens and eventually destroys the nail completely. This type of nail infection will not respond to nail lacquer treatment alone, but will require antifungal tablets or complete nail ablation by a podiatrist.
- An internal fungal infection of the nail plate is a relatively rare type of fungal nail infection. It does not necessarily in the beginning cause thickening, weakening and fragmentation of the nail or the typical blanched hornification under the nail plate. When a fungal infection within the nail plate continues long it often leads to dystrophy, i.e. withering of the nail. This, along with more serious variants of the above types of nail infection is known as TDO (Total Dystrophic Onychomycosis)
- Fungal nail infections caused by Candida albicans yeast are mostly the result of chronic paronychia or skin infection between the toes. Continuous humidity or use of rubber gloves or boots increases the risk of yeast infection. These types of infection are not common.