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Fungal Nail Infections - Onychomycosis

Basic Information on Fungal Nails


Updated July 03, 2014

Many people have thickened, discolored toenails and fingernails. About 50% of these abnormal nails are due to a fungal infection of the nail bed, matrix, or nail plate. The medical terms for this type of fungal infection are onychomycosis or tinea unguium. Fungal infections of the nail affect up to 3% of the population mainly in developed countries. Men are more often affected than women and usually later in life, after the age of 40.

Appearance of Fungal Nail Infections
There are actually 4 different types of fungal nail infections classified by the part of the nail involved. The most common infection involves the end of the nail when the fungi invade the hyponychium. Initially, the nail plate splits from the nail bed, a process called onycholysis. The end of the nail then turns yellow or white and keratin debris develops under the nail causing further separation. The fungus grows in the substance of the nail causing it to become fragile and crumble. The fungal organism responsible for most fungal nail infections is Trichophyton rubrum.

Risk Factors for Fungal Nail Infections
The following are instances that either promote infection with fungi or encourage growth of fungi:

  • Tight footwear promotes crowding of the toes keeps the toes warm and moist - a perfect environment for fungi to grow.
  • Exercise can cause repeated minor trauma to the hyponychium allowing fungi to invade.
  • Communal showers can expose the feet to fungi.
  • Diseases that influence the immune system like AIDS and diabetes can make it easier for a fungal infection to start.

Diagnosis of Fungal Nail Infections
Not every thickened, discolored nail is a fungal infection. Other diseases that can cause thickened nails are psoriasis, eczema, and lichen planus. It is important that fungal nail infections are diagnosed properly because treatment is long-term and expensive. Fungal nail infections are diagnosed by taking a sample of the debris under the nail. The most fungal elements are found under the nail and closest to the skin, therefore the nail should be trimmed before a sample is taken. There are two tests used to diagnose a fungal nail infection - the KOH test and a fungal culture. The KOH test has the advantage that it can be quickly performed. A fungal culture takes 3 to 4 weeks to come back, but can identify the exact fungal organism if there is any question.

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