Nail clubbing is a change in the appearance and structure of fingernails or toenails that can occur as a symptom of an underlying health condition. The following are some possible causes of nail clubbing:

• Low oxygen levels: Clubbing may result from chronic low blood-oxygen levels, which can be seen with cystic fibrosis, congenital cyanotic heart disease, and several other conditions.

• Heart and lung diseases: Clubbing often occurs in heart and lung diseases that reduce the amount of oxygen in the blood. These may include heart defects that are present at birth, chronic lung infections that occur in people with bronchiectasis, cystic fibrosis, or lung abscess, and lung disorders in which the deep lung tissues become swollen and then scarred (interstitial lung disease) .

• Liver and gastrointestinal diseases: Cirrhosis of the liver and other liver diseases, celiac disease, inflammatory bowel disease, and other conditions that cause inflammation in the digestive system can lead to clubbed nails.

• Other conditions: Other possible causes of nail clubbing include thyroid conditions, such as hyperthyroidism and Grave’s disease, and other types of cancer, including liver, gastrointestinal, Hodgkin lymphoma, and rhabdomyosarcoma.

It is important to note that nail clubbing can also be idiopathic or familial, meaning that it can occur without an underlying disease or be inherited. If you notice nail clubbing or any changes in your nails, it is recommended to see a healthcare provider, as it may be a sign of a health condition that needs treatment.