Caleb Foster
The white semicircles at the base of fingernails and toenails are called lunulae (singular: lunula, from the Latin for little moon). They are part of the nail matrix, the tissue at the base of the nail that contains nerves, lymph, and blood vessels and produces the cells that become the hardened nail plate. The lunula appears white because the epidermis is thicker beneath the matrix, blocking the pink colour from the blood vessels below. While white spots on the nails are usually not a cause for concern, sometimes they can indicate an underlying health condition.
| Characteristics | Values |
|---|---|
| Name | Half-moon, lunula (plural: lunulae) |
| Description | Rounded shadows at the base of the nails |
| Colour | White |
| Causes | Vitamin deficiency, vitiligo, kidney failure, or other health conditions |
| Formation | Injury to the nail matrix or bed |
| Concerns | Usually not a cause for concern, but a doctor should be consulted if there are any concerns or accompanying symptoms |
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What You'll Learn
The white semi-circles at the bottom of nails are called lunulae
The lunula is a very delicate part of the nail structure. If damaged, the nail will be permanently deformed. Even when the entire nail is removed, the lunula remains in place and is similar in appearance to another smaller fingernail embedded in the nail bed. In most cases, it is half-moon-shaped, but not everyone will have a lunula on each nail, and they may vary in appearance across each nail. They are usually most visible on the thumb, appearing smaller on the index finger and gradually shrinking in size until they are barely visible on the little finger.
Lunulae are usually white, but they can sometimes turn a different colour, which may indicate an injury or an underlying health condition. For example, blue lunulae can be a sign of Wilson's disease, a rare inherited disorder that occurs when too much copper accumulates in the body's organs. Red lunulae may be a signal of heart failure. However, small or missing lunulae are usually not cause for concern and are likely hidden underneath the cuticle or skin at the base of the finger.
White spots or lines on the nail, known as leukonychia, can be caused by injury to the nail or the bed underneath the nail. They may also be a sign of an underlying condition, such as hypoalbuminaemia (low albumin), kidney failure, liver failure, protein malabsorption, protein-losing enteropathies, or heavy metal poisoning. If someone has any concerns about white spots on their nails, they should consult a doctor.
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Lunulae are part of the nail matrix
The white circle underneath the fingernail, known as the lunula (pl. lunulae), is the crescent-shaped whitish area at the base of a fingernail or toenail. The word "lunula" comes from the Latin "little moon". Lunulae are part of the nail matrix, which is the tissue just beneath the nail that contains nerves, lymph, and blood vessels. The lunula is the part of the matrix that protrudes from under the skin of the finger.
The lunula is located at the end of the nail closest to the skin of the finger, but it still lies under the nail. It is not actually white but appears so when viewed through the nail. The epidermis is thicker beneath the matrix, which blocks the pink colour from the blood vessels below. In some people, the lunula barely protrudes and is only visible on the thumb and big toe.
The lunula is a delicate part of the nail structure, and damage to it will permanently deform the nail. Even when the entire nail is removed, the lunula remains in place and resembles a smaller fingernail embedded in the nail bed. In most cases, it is half-moon-shaped and has unique histologic features. While everyone has a nail matrix, not everyone will have a visible lunula on each nail. For those who do, the lunula may vary in appearance across each nail.
Lunulae are usually a whitish colour and take up a small portion of the bottom of the nail. They are typically most visible on the thumb, appearing smaller on the index finger, and gradually shrinking until they are barely visible on the little finger. Discoloured or missing lunulae are not usually a cause for concern. However, if you notice changes in nail appearance and experience other unusual symptoms, it is recommended to consult a doctor.
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White spots on nails can be caused by injury or an underlying condition
The white area at the base of the fingernail is called the lunula (pl.: lunulae), derived from the Latin word for "little moon". It is a delicate part of the nail structure, and damage to it can cause the nail to become permanently deformed. The lunula is usually white or whitish in colour, but it is not actually white; it only appears so when viewed through the nail. The epidermis beneath the matrix is thicker, which blocks the pink colour from the blood vessels below, resulting in the white appearance.
White spots on nails can be caused by injury to the base of the nail or an underlying condition. Doctors refer to these spots as "punctate leukonychia". They are typically the result of trauma to the nail, such as excessive nail-biting, tapping, or manicure procedures. In some cases, they may also be caused by heavy metal poisoning, most commonly by lead. These spots usually grow out on their own without treatment.
However, white spots on the nails can sometimes indicate other health issues. For example, they may be a sign of hypoalbuminaemia (low albumin), which is associated with nephrotic syndrome (a form of kidney failure), liver failure, protein malabsorption, or protein-losing enteropathies. In rare cases, they can also be a genetic condition, such as Darier disease or Hailey-Hailey disease.
If you are concerned about white spots on your nails, it is recommended to consult a healthcare professional. They can assess your symptoms and advise you on appropriate treatment options. Treating the underlying cause will typically restore your nail appearance and improve your overall health.
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In rare cases, white nails can be a genetic condition
The white circle underneath the fingernail, known as the lunula (pl.: lunulae), is the crescent-shaped whitish area of the bed of a fingernail or toenail. It is derived from the Latin word 'little moon'. In rare cases, white nails can be a genetic condition called leuconychia or leukonychia. Leuconychia is a rare nail disease that causes white discoloration on the entire nail and occurs on all nails. It is caused by a gene mutation and can be passed from one or both parents to their child. This condition is often present at birth or infancy.
Leukonychia is the medical term for white discoloration appearing on nails. It is derived from the Greek words 'leuko' meaning white and 'onyx' meaning nail. Leukonychia can be caused by a genetic condition or a side effect of taking sulphonamides, a family of antibiotics. By 2011, only 6 cases of non-hereditary leukonychia had been published. In familial cases, the condition is caused by mutations in the PLCD1 gene on chromosome 3p22.2, exhibiting an autosomal dominant pattern of inheritance, although sometimes it may be autosomal recessive.
Genetic linkage studies indicate that the gene defect underlying leuconychia resides on chromosome 12q13. As type II keratins map within this chromosomal interval, a mutation in one of these keratin genes may be the cause of hereditary leuconychia. The upper part of the nail plate, originating from the proximal nail matrix, has a non-homogeneous lamellar appearance with numerous intracellular 'lipidic' vacuoles and 'empty' spaces separating keratin filament bundles. These cells are shed at the nail surface, compensated by the hyperproliferation of the distal matrix and the nail bed keratinocytes.
Leuconychia can also be caused by rare disorders, including Bart-Pumphrey syndrome, which causes nail abnormalities, knuckle issues, and hearing loss; Bauer syndrome, which causes leuconychia and skin cysts; Buschkell-Gorlin syndrome, which causes nail problems, kidney stones, and skin cysts; and Darier disease (keratosis follicularis), which causes nail abnormalities and wart-like blemishes.
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A change in the colour or size of lunulae may indicate an underlying disease
The white circle underneath the fingernail, known as the lunula (pl.: lunulae) from the Latin 'little moon', is a crescent-shaped whitish area at the base of a fingernail or toenail. Lunulae are usually a whitish or ivory colour, and a healthy lunula should represent about one-fifth of the nail's length. However, a change in the colour or size of lunulae may indicate an underlying disease.
Colour
Red lunulae may signal heart failure, while blue lunulae could indicate a rare inherited disorder causing copper accumulation in organs, or a condition called cyanosis, resulting from poor circulation or inadequate oxygenation of the blood. Purple lunulae can also indicate poor circulation or respiratory issues. Lunulae that are reddish/pink may indicate diabetes or cardiovascular disease. Yellow lunulae could be a sign of problems with the lymphatic system, respiratory issues, diabetes, liver anomalies, or even tobacco use in smokers. Greenish-black discolouration may indicate a bacterial infection.
Size
Small lunulae, or microlunula, are considered abnormal and may indicate a weak immune system, frequent upper respiratory or urinary infections, or other illnesses that cause fatigue. Large lunulae, or macrolunula, may suggest chronic systemic diseases. Lunulae that are wide and out of proportion may signal excessive thyroid activity, hypertension, or heart disease.
Other factors
The number of lunulae may also be indicative of health issues. For instance, a person with only two lunulae on the thumbs may have average to low vitality and should consider better time management. In addition, the visibility of lunulae may vary with age, with older people experiencing a decrease in size and colour intensity.
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Frequently asked questions
The white circle at the base of a fingernail is called a lunula (plural: lunulae). It is the portion of the nail matrix that is visible and is usually white because the epidermis is thicker beneath the matrix, blocking the pink colour from the blood vessels below.
The lunula may disappear or become less visible due to vitamin deficiency, kidney failure, or another health condition. However, sometimes the lunulae are simply not visible, and their absence does not always indicate a serious health problem.
White spots on the fingernails are usually the result of a minor injury to the nail or nail bed. They can also be caused by fungal infections, mineral deficiencies, or, in rare cases, exposure to toxic heavy metals.
White spots on nails are usually not a cause for concern and will go away over time. However, if the spots appear with other symptoms or continue to develop, see a doctor as they may indicate an underlying health condition such as liver disease, anemia, or an allergic reaction.
