Nail clubbing happens when soft tissue in the ends of the fingers swells and changes the shape of the nails. It is sometimes a sign of lung cancer or another health condition that may require treatment.
Other names for this condition are finger clubbing and digital clubbing.
Nail clubbing typically affects the fingers on both hands. It may also affect the toes.
Clubbed nails leave the skin at a larger angle than usual, which causes them to curve more than usual.
The affected nails or tips of the fingers or toes may appear larger, wider, or more swollen or bulgy. The tips of the fingers or toes may also be warm and red or darker in color than usual.
People with nail clubbing
If a person notices nail clubbing or other changes to their nails, experts recommend contacting a doctor. A doctor can help the person identify the cause and recommend treatment.
Read on to learn more about nail clubbing and lung cancer.
Clubbed nails follow an unusual curve from the base of the nail to the tip.
The clubbing may range from minimal to severe.
Doctors
Lovibond angle
The Lovibond angle is the angle between the nail base and bordering skin, or nail fold.
People without nail clubbing typically have Lovibond angles less than 180 degrees.
Clubbed nails have Lovibond angles greater than 180 degrees.
Hyponychial angle
The hyponychial angle is the angle between two imaginary lines.
The first line runs from the nail cuticle to the distal digital crease, or the crease of the joint closest to the nail. The second line runs from the cuticle to the hyponychium, which is the skin under the tip of the nail.
People without nail clubbing typically have hyponychial angles less than 192 degrees.
Clubbed nails have hyponychial angles greater than 192 degrees.
Phalangeal depth ratio
The phalangeal depth ratio is the ratio between the depth of the finger at the base of the nail and the depth at the distal interphalangeal joint, or the joint closest to the nail.
People without nail clubbing typically have phalangeal depth ratios of less than 1. The depth of their fingers is smaller at the base of their nails than at the joints closest to the nails.
When nail clubbing occurs, the phalangeal depth ratio is greater than 1. The depth of the fingers is greater at the base of the nails than at the joints closest to the nails.
Schamroth sign
A doctor may check for the Schamroth sign by asking someone to press the upper surface of the joint closest to the nail on one finger against the same area of the same finger on the other hand.
This typically causes a diamond-shaped space to appear between the fingers, known as the Schamroth sign or Schamroth window.
Nail clubbing does not produce a diamond-shaped space.
Lung cancer is a common cause of nail clubbing.
Roughly
Nail clubbing may also be a sign of another health condition, such as:
- other types of lung disease, like pulmonary fibrosis
- other types of cancer that cause tumors in the chest
- cardiovascular disease
- intestinal disease
- liver disease
- infection
Sometimes nail clubbing is hereditary or has no known cause.
Experts are still researching the exact cause of nail clubbing in lung cancer. However, they believe increased vascular endothelial growth factor (VEGF) plays a role.
VEGF is a signaling protein that stimulates the growth of new blood vessels. It also increases capillary permeability. This allows molecules to pass more easily through small blood vessel walls.
Platelets, megakaryocytes, and many other types of cells release VEGF. Platelets are cells that help form blood clots. Megakaryocytes are cells that form platelets.
Abnormal blood vessel formation, low oxygen levels, and chronic inflammation in people with lung cancer may cause immature platelets or megakaryocytes to release more VEGF than usual.
It is possible that lung cancer cells may also release VEGF.
Increased VEGF may contribute to changes in fingers or toes that lead to nail clubbing, such as:
- increased capillary density, or growth of more small blood vessels
- increased capillary dilation, or widening of small blood vessels
- edema, or fluid buildup
- connective tissue changes
Other signaling proteins, such as platelet-derived growth factor (PDGF) or prostaglandin E2, may also contribute to changes that lead to nail clubbing.
It is possible that lung cancer treatment may help reverse nail clubbing due to lung cancer and improve other lung cancer symptoms.
Certain types of cancer medications may also cause nail changes unrelated to nail clubbing.
These changes may include:
- reduced nail growth or pauses in nail growth
- grooves, ridges, lines, or discoloration of the nail
- onycholysis, or separation of the nail from the nail bed
- paronychia, or nail infection
- bleeding under the nail
- a dark spot on the cuticle
- loss of the nail
A doctor can discuss how cancer treatments may specifically affect a person’s nails, including potential improvements in nail clubbing or other changes to the nails.
A person should let their doctor know if they develop changes to their nails. The doctor can help them learn whether lung cancer, cancer treatments, or other factors may be responsible.
Treatments for nail clubbing focus on the underlying cause of the condition.
If a person has lung cancer, treating the cancer may help improve symptoms such as nail clubbing.
A person’s treatment for lung cancer depends on several factors, such as:
- the specific type of lung cancer
- the location and size of lung cancer tumors
- whether the cancer has spread
- their age and overall health
- their goals and preferences
A person can talk with their doctor to learn about their cancer treatment options and how those treatments may affect nail clubbing or other symptoms.
A person should let a doctor know if they think they might have nail clubbing.
Nail clubbing is sometimes a sign of lung cancer or another serious health condition.
A doctor will ask about the person’s symptoms and medical history. They may also order tests to check for lung cancer or other potential causes of nail clubbing. Sometimes the cause may be unidentifiable.
A doctor can help a person learn about their treatment options and outlook if the nail clubbing is caused by lung cancer or another underlying health condition.
Nail clubbing occurs when swelling in the end of the fingers or toes changes the shape of the nail. The surrounding flesh or nearby joints may also be warm, inflamed, or painful.
Nail clubbing may be a sign of lung cancer or another serious health condition.
Sometimes nail clubbing is hereditary or has no known cause.
A person should let a doctor know if they think they might have nail clubbing.
A doctor can help them learn what is causing the nail clubbing and recommend treatment.