Introduction to fungal nails — I

Many changes in fingernails or toenails may cause people to think they have a fungal infection of the nails, medically known as onychomycosis.

Fungal infection of the nails sometimes makes the condition sound contagious or related to poor hygiene. In fact, up to 10% of all adults in Western countries have fungal infection of the nails. This percentage increases to 20% of adults who are age 60 or older. Toenail fungus is much more common than fingernail fungus.

In reality, abnormal-looking nails may be caused by a number of conditions including, but not limited to, fungal infection. There are many other reasons why your nails may look different.

What are the symptoms and signs of fungal nails?Although fungal nails are usually cosmetic concerns, some patients do experience pain and discomfort. These symptoms may be exacerbated by footwear, activity, and improper trimming of the nails.

There are many species of fungi that can affect nails. By far the most common, however, is called Trichophyton rubrum. This type of fungus has a tendency to infect the skin (known as a dermatophyte) and manifests in the following specific ways.

* Starts at the ends of the nails and raises the nail up: This is called “distal subungual onychomycosis.” It is the most common type of fungal infection of the nails (90%). It is more common in the toes than the fingers, and the great toe is usually the first one to be affected. Risk factors include older age, swimming, athlete’s foot, psoriasis, diabetes, family members with the infection, or a suppressed immune system. It usually starts as a discolored area at a corner of the big toe and slowly spreads toward the cuticle. Eventually, the toenails will become thickened and flaky. Sometimes, you can also see signs of athlete’s foot in between the toes or skin peeling on the sole of the foot.

* Starts at the base of the nail and raises the nail up: It is called “proximal subungual onychomycosis.” This is the least common type of fungal nail (3%). It is similar to the distal type, but it starts at the cuticle (base of the nail) and slowly spreads toward the nail tip. This type almost always occurs in people with a damaged immune system.

* Yeast onychomycosis: This type is caused by a yeast called Candida and not by the Trichophyton fungus named above. It is more common in fingernails and is a common cause of fungal fingernails. Patients may have associated paronychia (infection of the cuticle). Candida can cause yellow, brown, white, or thickened nails. Some people who have this infection also have yeast in their mouth or have a chronic paronychia (see above) that is also infected with yeast.

What tests do health-care professionals use to diagnose fungal nails?

Physical exam alone has been shown to be an unreliable method of diagnosing fungal nails. There are many conditions that can make nails look damaged, so even doctors have a difficult time. In fact, studies have found that only about 50%-60% of cases of abnormal nail appearance were caused by fungus. Therefore, laboratory testing is almost always indicated. Some insurance companies may even ask for a laboratory test confirmation of the diagnosis in order for antifungal medicine to be covered. A nail sample is obtained either by clipping the toenail or by drilling a hole in the nail. That piece of nail is sent to a lab where it can by stained, cultured, or tested by PCR (to identify the genetic material of the organisms) to identify the presence of fungus. Staining and culturing can take up to six weeks to get a result, but PCR to identify the fungal genetic material, if available, can be done in about one day. However, this test is not widely used due to its high cost. A negative biopsy result with high clinical suspicion warrants a repeat test due to the prevalence of false-negative results in these tests.

— medicinenet.com

to be continued