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| ICD9 = | ICDO = | OMIM = | MedlinePlus = 001330 | eMedicineSubj = derm | eMedicineTopic = 300 | MeshID = D014009Onychomycosis means fungal infection of the nail. It is the most common disease of the nails and constitutes about a half of all nail abnormalities.This condition may affect toe- or fingernails, but toenail infections are particularly common. The prevalence of onychomycosis is about 6-8% in the adult population. Onychomycosis caused by dermatophytes is also known as tinea unguium (tinea of the nails).
Symptoms The nail plate can have a thickened, yellow, or cloudy appearance. The nails can become rough and crumbly, or can separate from the nail bed. There is usually no pain or other bodily symptoms, unless the disease is severe. http://www.emedicine.com/derm/topic300.htmDermatophytids are fungus-free skin lesions that sometimes form as a result of a fungus infection in another part of the body. This could take the form of a rash or itch in an area of the body that is not infected with the fungus. Dermatophytids can be thought of as an allergic reaction to the fungus.
Causes The causative pathogens of onychomycosis include dermatophytes, Candida, and non-dermatophytic moulds. Dermatophytes are the fungi most commonly responsible for onychomycosis in the temperate western countries; meanwhile, Candida and non-dermatophytic moulds are more frequently involved in the tropics and subtropics with a hot and humid climate.Chi CC, Wang SH, Chou MC. The causative pathogens of onychomycosis in southern Taiwan. Mycoses 2005; 48: 413-420. [http://www.ncbi.nlm.nih.gov/pubmed/16262878?ordinalpos=2&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum] Trichophyton rubrum is the most common dermatophyte involved in onychomycosis. Other dermatophytes that may be involved are Trichophyton interdigitale, Epidermophyton floccosum, Trichophyton violaceum, Microsporum gypseum, Trichophyton tonsurans, Trichophyton soudanense (considered by some to be an African variant of T. rubrum rather than a full-fledged separate species) and the cattle ringworm fungus Trichophyton verrucosum. A common outdated name that may still be reported by medical laboratories is Trichophyton mentagrophytes for T. interdigitale. The name T. mentagrophytes is now restricted to the agent of favus skin infection of the mouse; though this fungus may be transmitted from mice and their danders to humans, it generally infects skin and not nails. Other causative pathogens include Candida and non-dermatophytic moulds, in particular members of the mould genera Scytalidium (name recently changed to Neoscytalidium), Scopulariopsis, and Aspergillus.
Candida mainly cause fingernail onychomycosis in people whose hands are often submerged in water. Scytalidium mainly affects people in the tropics, though it persists if they later move to areas of temperate climate. Other moulds more commonly affect people olders than 60 years, and their presence in the nail reflects a slight weakening in the nail's ability to defend itself against fungal invasion.
Classification ; Distal Subungual Onychomycosis: The most common form of tinea unguium usually caused by Trichophyton rubrum, which invades the nail bed and the underside of the nail plate.
; White Superficial Onychomycosis: Caused by fungal invasion of the superficial layers of the nail plate to form "white islands" on the plate. Accounts for only 10 percent of onychomycosis cases.
; Proximal Subungual Onychomycosis: Fungal penetration of the newly formed nail plate through the proximal nail fold. It is the least common form of tinea unguium in healthy people but found more commonly when the patient is immunocompromised.
; Candidal Onychomycosis: Candida species invade fingernails usually occurring in persons who frequently immerse their hands in water. This normally requires the prior damage of the nail by infection or trauma.
; Total Dystrophic Onychomycosis: Total destruction of the nail plate. It is the end result of any of the above four types.
Diagnosis If all nails are affected then fungal infection is improbable. To avoid misdiagnosis as psoriasis, lichen planus, contact dermatitis, trauma, nail bed tumor or yellow nail syndrome, laboratory confirmation may be necessary. The three main approaches are potassium hydroxide smear, culture and histology. This involves microscopic examination and culture of nail scrapings or clippings. Recent results indicate that the most sensitive diagnostic approaches are direct smear combined with histological examinationPMID 17222296 and nail plate biopsy using periodic acid-Schiff stainPMID 12894064.
Treatment Treatment of onychomycosis is challenging because the infection is embedded within the nail and is difficult to reach. As a result full removal of symptoms is very slow and may take a year or more.
Pharmacologic RxMost treatments are either systemic antifungal medications such as terbinafine and itraconazole, or topical such as nail paints containing ciclopirox or amorolfine. There is also evidence for combining systemic and topical treatments.For superficial white onychomycosis systemic rather than topical antifungal therapy is advised.
Natural remediesAs with many diseases, there are also some scientifically unverified folk or alternative medicine remedies.
Relative effectiveness of treatmentsIn July 2007 a meta-study reported on clinical trials for topical treatments of fungal nail infections. The study included 6 randomised controlled trials dating up to March 2005. The main findings are:
Drug pipelineMost drug development activities are focused on
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