Onychomycosis
From Wikipedia, the free encyclopedia
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|---|---|
| A toenail affected by Onychomycosis | |
| ICD-10 | B35.1 |
| ICD-9 | 110.1 |
Onychomycosis means fungal infection of the nails. It represents up to 20% of all nail disorders.
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.[1] The most common type of onychomycosis (80-90%), caused by dermatophytes, is technically known as tinea unguium (tinea of the nails).[2]
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[edit] Causes
Dermatophytes are the fungi most commonly responsible for onychomycosis. Two dermatophyte species, Trichophyton rubrum and Trichophyton interdigitale, cause the vast majority of onychomycosis cases worldwide. Other related dermatophyte fungi that may be involved are 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 A common outdated name that may still be reported by medical laboratories is Trichophyton mentagrophytes for T. interdigitale.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 causal fungi include yeasts (5-17%), e.g., Candida, and non-dermatophytic moulds, in particular members of the mould genera Scytalidium (name recently changed to Neoscytalidium), Scopulariopsis, and Aspergillus.
Yeasts 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 mainly affect people over the age of 60, and their presence in the nail reflects a slight weakening in the nail's ability to defend itself against fungal invasion.
[edit] Treatment
Treatments are usually commenced after laboratory confirmation of fungal invasion based on microscopic examination and culture of nail scrapings or clippings. Systemic antifungal medications such as terbinafine and itraconazole have been shown to be effective in treating it, as have some topical nail paints, such as one containing ciclopirox.
[edit] Natural remedies
As with many diseases, there are also some scientifically unverified folk or alternative medicine remedies.
- Tea tree oil is a known antifungal. The topical application of high levels is a verified remedy for some dermatophytic skin infections although not for onychomycosis, where the fungus is often too deeply nested in dense subsurface nail tissue to be full expunged by topically applied materials of any kind. [1].
- Grapefruit seed extract as a natural antimicrobial is not demonstrated. Its effectiveness is scientifically unverified. Multiple studies indicate that the universal antimicrobial activity is due to contamination with synthetic preservatives that were unlikely to be made from the seeds of the grapefruit[2][3][4][5][6]
- Distilled white vinegar[citation needed]. Drops are applied to the cuticle twice a day. This method does not kill the fungus, but the vinegar allegedly changes the pH (acid content) of the new nail formed in that 12-hour period. (The scientific perspective, however, is that vinegar is unlikely to penetrate the dense keratinous tissue thoroughly enough to have any significant effect. Instead, it may be absorbed by the skin above the nail and work its way to where the nail is actually forming.) As the old, infected nail grows and is cut away, it is said to be replaced by an acidic nail, uninhabitable by fungi. Several months of consistent application are involved.
[edit] Relative Effectiveness of Treatments
A 2000 study assessed the effects of different topical treatments for fungal infections of the skin and nails of the foot. The study reviewed 72 randomized clinical trials dating up to December 1997. The main findings were:
- allylamines, azoles and undecenoic acid were efficacious.
- allylamines cured slightly more infections than azoles, but were much more expensive.
- the most cost-effective strategy was first to treat with azoles or undecenoic acid, and to use allylamines only if that failed.
A 2002 study compared the efficacy and safety of terbinafine in comparison with placebo, itraconazole and griseofulvin in treating fungal infections of the nails. The main findings were that for reduced fungus terbinafine was found to be significantly better than itraconazole and griseofulvin, and terbinafine was better tolerated than itraconazole.
A small study showed that ciclopirox nail paint was more effective when combined with topical urea cream.[7]
Another medicinal lacquer, NM100060 from NexMed, has commenced Phase III clinical trials in the United States; treatment contains terbinafine as the active ingredient and the trial involved comparison to Lamisil creme.[8] Commercial sale of the product is expected to begin no earlier than in 2008. [5]
[edit] References
- ↑ Cochrane Database Syst Rev. 2000;(2):CD001434. PMID 10796792
- ↑ Br J Dermatol. 2002 Jul;147(1):118-21. PMID 12100193
- ^ Nenoff P, Haustein UF, Brandt W (1996). "Antifungal activity of the essential oil of Melaleuca alternifolia (tea tree oil) against pathogenic fungi in vitro". Skin Pharmacol. 9 (6): 388-94. PMID 9055360.
- ^ von Woedtke T; Schluter B; Pflegel P; Lindequist U; Julich WD. Aspects of the antimicrobial efficacy of grapefruit seed extract and its relation to preservative substances contained. Institute of Pharmacy, Ernst Moritz Arndt University, Greifswald, Germany. Pharmazie (1999) June;54(6):452-6 PMID 10399191
- ^ Sakamoto S, Sato K, Maitani T, Yamada T. Analysis of components in natural food additive "grapefruit seed extract" by HPLC and LC/MS Eisei Shikenjo Hokoku. 1996;(114):38-42. PMID 9037863
- ^ PMID 11453769
- ^ PMID 16159196
- ^ PMID 16719494
- ^ Mitchel L. Zoler. "Boosts drug entry into nails: urea, ciclopirox combo tested for onychomycosis.(Focus on Skin Disorders)", Internal Medical News, April 1, 2004, pp. 69.
- ^ Staff. "Clinical Trials Update", Genetic Engineering News, September 15, 2005, pp. 5.
