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Does Fungus Cause My Black Toenail?
If you have noticed that one or several toenails have turned black, it is normal to ask yourself about the cause behind the problem. While a fungal infection is the main culprit in most situations, other causes can lead to similar changes.
Getting a correct diagnosis is essential, especially since a black toenail can also represent a sign of cancer (malignant melanoma). The sooner an adequate diagnosis is made, the sooner the right treatment can be started.
Chromonychia, a term that includes all nail color changes
According to the Text Atlas of Nail Disorders[1], chromonychia is a term generally used to describe all changes that occur at the level of a nail in terms of color. The affectation can refer to both the surface of the nail and the subungual tissues. There are a number of factors to be considered here, such as the previous transparency of the nail, its state of health, and the underlying tissues.
It is important to understand that a number of causes, including the excessive production of melanin, can lead to the excess accumulation of pigment at the nail level.
The accumulation of hemosiderin, copper, or various drugs can also modify the color of the toenails. If the skin vessels are affected or the person suffers from underlying conditions, such as anemia, the color of the nails may also change. The same goes for those who have suffered from carbon monoxide poisoning.
When visiting the dermatologist, he/she will examine the toenails to determine the exact cause behind color changes. During the examination process, it is important to keep the toes relaxed and not pressed hard against the floor (this will influence the color of the nail bed).
Melanonychia or when your nails turn a black/brown color
Melanonychia is a term used to describe nails that have turned black or brown. As the authors of the Text Atlas of Nail Disorders [1] point out, it is important to consider such changes, as one of the potential causes is malignant melanoma.
What are the other causes of black toenails? The list includes exposure to silver nitrate, injury/trauma resulting in hemorrhage, fungal infections, naevi, race, or taking certain drugs, such as doxorubicin or cyclophosphamide.
A particular form is a longitudinal melanonychia, characterized by a longitudinal black line on the nail’s surface. This change can be idiopathic, but it is also present in dark-skinned individuals without being a pathologic sign.
People who suffer from various underlying conditions can present such characteristic changes: Addison’s disease, Cushing’s disease (followed by removal of adrenal glands), cancer (breast), drugs, exposure to radiation, digestive disorders (malnutrition), and treatment against cancer (chemotherapy).
Pregnant women, those who have been diagnosed with secondary syphilis, or those who present vitamin B12 deficiency can also present longitudinal melanonychia.
Several dermatological conditions, including primary amyloid, basal cell carcinoma, and toenail bacterial infections, can lead to such changes. Lichen planus, Bowen’s disease, porphyria, and radiodermatitis are also on that list. Radiotherapy, as a form of treatment, can lead to melanonychia, especially when performed on a long-term basis. Melanonychia is also encountered in those with frequent or acute injuries.
Longitudinal melanonychia can also affect children. According to a study[2] published by the US National Library of Medicine, such changes are caused by lentigo or nevus. The study involved children under the age of 16 and confirmed that such changes are always benign (no cases of malignant melanoma were identified).
Another study[3], also published in the US National Library of Medicine, discussed longitudinal melanoma as being caused either by melanocyte activation (excess production of melanin) or proliferation (as it happens in patients diagnosed with malignant melanoma, nevus, or lentigo). The authors of the study highlighted that matrix biopsy is essential for confirming the diagnosis (especially when a malignant biopsy is concerned).
The correct diagnosis is more important than you might think.
Yes, your black toenail could be caused by a fungal infection. But, at the same time, you could suffer from malignant melanoma (one of the most dangerous forms of cancer). The doctor can make a correct diagnosis by performing a thorough medical examination, taking your medical history (other family members diagnosed with cancer), and performing a biopsy (if the suspicion of cancer is valid).
There are a number of signs that can indicate a fungal infection. For example, the affected toenail is brittle, thickened, and discolored. The skin around it is scaly, and a foul odor comes from the respective area. Purulent discharge can appear, and, in more severe cases, the nail can become loose (and even completely detached).
Discolored nails are almost always a sign of fungal infections, especially if accompanied by the abovementioned symptoms. Left untreated, the fungus will spread, attacking the nail and the nail bed. The discoloration will only progress until the nail turns darker (black).
As you might know, injuries expose the toenails, increasing the risk of fungal infections. This practically creates a vicious circle—the fungal infection affects the health of the toenails, leaving them prone to injuries, which further reinforces the power of the fungus. Fungal infections are treated with topical creams and medicated nail polishes, oral medication (Lamisil), and laser therapy. Removal is recommended in severe cases, followed by the antifungal treatment of the nail bed.
Malignant melanoma, on the other hand, presents different symptomatology. In the majority of cases, only one digit is affected, and the pigmentation spreads to the periungual area. Moreover, the initial band continues to darken as the condition progresses (with the borders becoming blurred with the passing of time). The correct diagnosis is more important than you might think; misdiagnosis can delay the adequate treatment, given the tumor time to spread and reach a life-threatening stage.
Patients suffering from malignant melanoma can present black stripes or spots on their toenails. The blurred borders are not a positive sign, suggesting the condition has advanced. The same goes for the longitudinal line, which becomes thicker, wider, and darker in color.
Unfortunately, in a lot of cases, cancer begins in the nail matrix, taking a lot of time before it is correctly diagnosed (in most situations, the discoloration is attributed to a fungal infection). A family history of cancer can guide the doctor in the right direction.
According to a study[4] published in the Brazilian Dermatological Journal, the dermatoscopic examination of the nail matrix and bed is essential for an accurate and early diagnosis. It is highlighted that such examinations can allow for cases of malignant melanoma to be diagnosed as early as possible, thus guaranteeing the best prognosis for the patient in question. Once the diagnosis has been made, the patient must undergo chemotherapy or radiotherapy. The amputation of the affected toe can guarantee the best prognosis, as it will ensure that cancer will not spread further.
Other causes of black toenails
If the toenails have a greenish-black discoloration, this is a sign that the patient might suffer from an infection with pseudomonas aeruginosa. These infections are difficult to treat due to their high resistance to treatments.
It has been briefly mentioned that trauma or injuries can cause toenails to become black. This is quite true. The appearance of the affected toenail is caused by damaged blood vessels. As the blood collects under the nail bed, it will cause the toenail to appear red, blue, or even purple. The nail may turn black as the nail begins to heal and the blood is resorbed. It may also be painful and detached from the nail bed (partially/totally).
The most common situation is when a heavy object is dropped on a person’s foot. The pain is most intense immediately after the injury, accompanied by a pulsating sensation. However, it is important to understand that repetitive trauma can lead to such problems. For example, if a person wears shoes that are too tight, the constant pressure can damage blood vessels, causing one’s toenails to turn black. Similar problems are encountered in professional athletes because the forefoot constantly hits the shoe.
Remember that injured toenails present a high risk for fungal infections, so keeping them dry and clean is important. You might also want to use antifungal powder for preventative purposes. In the situation that an injury has occurred at the level of the toenails, there are not many things that you can do, as such injuries often heal by themselves. Maintaining excellent foot hygiene will stimulate a faster and more efficient healing process.
If you experience intense pain, as well as a sensation of pressure or bleeding at the nail’s level, the doctor might decide to remove the affected nail and treat the nail bed against infection. As an alternative to the removal, he/she might drill a small hole in the toenail to provide the blood with an exit point and reduce the pain and pressure experienced.
Verdict: does fungus cause my black toenail?
Yes, your black toenail can be caused by a fungal infection. If you suspect such a problem has occurred, it is time to visit your dermatologist and get a correct diagnosis. As you have seen, other conditions can modify the color of your toenails, so you should seek a specialist to be certain of the underlying problem.
References:
[1] A Text Atlas of Nail Disorders, Martin Dunitz, 2003. Retrieved from: http://www.rusmedserv.com/mycology/html/Atlas_of_Nail_Disorders.pdf
[2] Longitudinal melanonychia in children: a clinical and histopathological study of 40 cases. US National Library of Medicine. 1999. Retrieved from: http://www.ncbi.nlm.nih.gov/pubmed/10411404
[3] Tangential biopsy thickness versus lesion depth in longitudinal melanonychia: a pilot study. US National Library of Medicine. 2012. Retrieved from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3312251/
[4] Melanonychia: the importance of dermatoscopic examination and of nail matrix/bed observation. 2009. Brazilian Dermatological Journal, vol.84, no.2. Retrieved from: http://www.scielo.br/scielo.php?pid=S0365-05962009000200013&script=sci_arttext&tlng=en