Nail clubbing is a uniform swelling of the soft tissue of the finger which leads to loss of the angle of the nailbed. There is increase in convexity of the nail fold and also thickening at the distal aspect of the finger.
There many causes of nail clubbing, including the following:
Respiratory: bronchiectasis; cystic fibrosis; sarcoidosis; empyema; interstitial lung disease; idiopathic pulmonary fibrosis
Cardiac: aortic aneurysm; Eisenmenger syndrome; cyanotic congenital cardiac disease; bacterial endocarditis
Gastrointestinal: inflammatory bowel disease; liver cirrhosis; primary biliary cirrhosis