Leukonychia, is a medical term for white discolouration appearing on nails. It is derived from the Greek words leuko and onyx. The most common cause is injury to the base of the nail where the nail is formed.
Types
Leukonychia totalis
This condition consists of a whitening of the entire nail and mostly likely occurs on all nails. Whitening of one, and only one, entire nail is not recognized as a symptom of Leukonychia totalis but as a likely result of mechanical trauma. Leukonychia totalis may be a clinical sign of hypoalbuminaemia, which can be seen in nephrotic syndrome, liver failure, protein malabsorption and protein-losing enteropathies. A genetic condition or a side effect from taking sulphonamides can also cause this appearance. By 2011, only 6 cases of non-hereditary also Leukonychia totalis were published.
Leukonychia partialis
This condition consists of a whitening of parts of the nail plate in the form of small white dots. There are three different variations of partial leukonychia; punctate, transverse and longitudinal leukonychia. Some of the more serious variations of leukonychia partialis may lead to leukonychia totalis.
Leukonychia striata
Leukonychia striata, transverse leukonychia, or Mees' lines are a whitening or discoloration of the nail in bands or "stria" that run parallel the lunula. This is commonly caused by physical injury or disruption of the nail matrix. Common examples include excessive biting or tapping of the nails, trauma or injury from accidents involving doors or windows, and extensive use of manicure. It may also occur in great toenails as a result of trauma from footwear. Alternatively, the condition can be caused by heavy metal poisoning, most commonly by lead. Finally, it can be caused by cirrhosis of the liver or chemotherapy. The tendency toward leukonychia striata is sometimes inherited in an autosomal dominant fashion. In other cases, it can be attributed to vigorous manicuring and trauma aforementioned, or to a wide variety of systemic illnesses. Serious infections known for high fevers, measles, malaria, herpes, and leprosy may also cause this condition. In many patients, there is no obvious cause, and the streaks resolve spontaneously. There is a similar condition called Muehrcke's lines which differs from leukonychia in that the lines fade with digital compression and does not migrate with the growth of the nail.
Leukonychia punctata
Also known as "true" leukonychia, this is the most common form of leukonychia, in which small white spots appear on the nails. Picking and biting of the nails are a prominent cause in young children and nail biters. Besides parakeratosis, air that is trapped between the cells may also cause this appearance. It is also caused by trauma. In most cases, when white spots appear on a single or a couple of fingers or toes, the most common cause is injury to the base of the nail. When this is the case, white spots disappear after around eight months, which is the amount of time necessary for nails to regrow completely. The pattern and number of spots may change as the nail grows.
Longitudinal leukonychia
Longitudinal leukonychia is far less common and features smaller 1mm white longitudinal lines visible under the nail plate and parallel to the nail bed. It may be associated with Darier's disease.
Cause
It is harmless and most commonly caused by minor injuries, such as nail biting, which occur while the nail is growing. Leukonychia occurs most commonly in healthy individuals, and is unrelated to any known nutritional or physiological deficiency. When caused by injury the marks will disappear as the nail grows outwards. While there are various sources that link dietary needs or vitamin deficiency with recurrent leukonychia, this notion has been challenged by some medical researchers. Other possible reasons for this problem with nail colour can be linked to:
