Tinea Unguium

What is Tinea Unguium

Tinea unguium, also called onychomycosis is a contagious fungal infection of the nail tissue which can affect both finger and toenails. It is a common disease affecting about 14% of the adult population and can be caused by dermatophytes (fungi living on the skin), nondermatophyte types of molds or yeasts.

Tinea Unguium symptoms

Epidemiology: tinea unguium is the most commonly found nail disease. It has a greater prevalence in older people and shows an increasing rate of incidence (also in younger people and children). Probably, the increased prevalence reflects the widespread usage of immunosuppresive drugs, usage of locker rooms and wearing of modern, tight shoes. Even though it can affect almost anyone, some are at greater danger of catching this type of infection. Predisposing factors include the HIV infection, diabetes (one third of diabetics is supposed to be affected) and poor peripheral circulation. Wearing artificial nails has also been implicated as a factor in the pathogenesis. It’s a bit more common in men and in people living in urban areas of the world.

Once the infection is acquired, it will not heal spontaneously and because of that, the incidence increases with age.

Commonly, the infection of the nails is preceded by tinea pedis (fungal infection of the skin on feet) from where the pathogens can easily invade the nail tissue and act as a reservoir for other kinds of tineas (on the body, groin, scalp etc.).

Tinea Unguium pictures

tinea unguium pictures

Photo Credit: http://www.treatmentforonychomycosis.com/

Aetiology: in most of the patients, the infection can be attributed to the next species of fungi: Trichophyton rubrum, Trichophyton interdigitale (these two are found in about 90% of the cases), Trichophyton tonsurans and Epidermophyton floccosum. Just about 10% of the toenail infections are caused by other organisms (nondermatophyte molds and yeasts) like: Acremonium, Aspergillus, Fusarium, Scopulariopsis brevicaulis and Scytalidium. About 30% of all the fingernails infections are caused by Candida spp.

Transmission: is similar to all the other ringworm tinea infections. The organisms can invade the nails after a direct contact with an infected individual or with items that contain infected particles of skin (common transmission between family members). Some species live in the environment and are not transmitted between humans.

Clinical manifestation of onychomycosis: about 80% of nail fungal infections occur on toe nails (especially the big toes).

There are four classic types of onychomycosis:

  • The distal lateral subungual onychomycosis: where a white patch is visible on the distal or lateral undersurface of the nail and the nail bed. If the infection is not treated, the nail becomes opaque, thickened, cracked and raised. It is the most common form of onychomycosis.
  • The white superficial onychomycosis: where on the proximal nail plate there is a white, chalk like plaque. This type is almost never seen on the fingernails, just on the toenails. It is sometimes misdiagnosed as keratin granulations (a reaction to nail polish). The distal lateral subungual and the white superficial type can coexist at the same time.
  • The proximal subungual onychomycosis: which occurs usually on the toenails and looks like a white spot. With time, the spot moves distally and can involve most of the undersurface of the nail. It is more commonly found in immuno compromised patients (patients with this type of disease should be screened for HIV).
  • The Candida onychomycosis: where Candida is the offending organism. Prior to the infection, usually there has been trauma or infection of the nails.

Differential diagnosis: tinea unguium can sometimes look a lot like psoriasis, eczema, Reiter syndrome, onycogryphosis, some congenital nail dystrophies, chemical or traumatic injuries to nails, lichen planus, yellow nail syndrome and Darier-White syndrome.

Diagnosis: with onychomicosis, clinical diagnosis (just by looking at the nails) is usually not enough. The doctor has to take a bit of the nail to examine it under a microscope or plant it into a medium to grow a fungal culture.

Treatment: of the nails infected with fungi is difficult because the organisms that cause the infection are inside the tissue and difficult to reach. In order for the nail to be truly healthy, a new one must completely replace the old one. The medications used in the treatment are anti fungals, which can be taken orally or applied topically.

  • Topical agents (available as lotions or lacquers) are usually just moderately effective. They have to be applied for a long time (about a year) and include ciclopirox nail paint amorolfine and efinaconazole. Even if topical therapy alone is not considered adequate, it might be an option in patients who cannot take systemic treatment.
  • Systemic agents include terbinafine, itraconazole and fluonazole. The indications for prescribing these type of drugs include affected fingernails, limited function of the infected part, pain, a greater potential for bacterial infections, physical and other disabilities.
  • Removing the diseased part of the infected nails is advised.

Prognosis: as mentioned before, fungal infection of the nails will not go away if not treated. The pathogens will gradually spread to other toenails and skin areas (body, groin, hands). Because of the disease, the protective barrier of the skin is damaged and other organisms (like bacteria) can enter into the blood easily (happens frequently after a vein from the leg has been taken in a heart operation). Even after a successful course of treatment, the infection can often reoccur. Diabetic patients are at a significantly greater risk of having fungal nail infections and should be screened regularly.

Prevention: it is important to keep the feet dry and clean. The toenails should be regularly clipped and one should avoid walking bare feet in areas where the infection is possible (locker rooms,swimming, bathing areas). Shoes must allow the feet to breathe and mustn’t be too tight.

References

Arnold, Harry L, Odom, Richard B, James, William D and Andrews, George Clinton, 1990, Andrews’ diseases of the skin. Philadelphia : Saunders.

Fitzpatrick, Thomas B and Freedberg, Irwin M, 2003, Fitzpatrick’s dermatology in general medicine. New York : McGraw-Hill, Medical Pub. Division.

Rook, Arthur and Burns, Tony, 2010, Rook’s textbook of dermatology. Chichester, West Sussex, UK : Wiley-Blackwell.

Wolff, Klaus, Johnson, Richard Allen and Fitzpatrick, Thomas B, 2009, Fitzpatrick’s color atlas and synopsis of clinical dermatology. New York : McGraw-Hill Medical.

http://www.medicinenet.com/script/main/art.asp?articlekey=5798

http://www.medicinenet.com/image-collection/ringworm_tinea_unguium_onychomycosis_picture/picture.htm

http://en.wikipedia.org/wiki/Onychomycosis

http://www.medscape.com/viewarticle/807034_3

 

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