In clubbing, the fingertips and ends of the toes become broader, thicker, and bulbous, and there is increased curvature of the nails so that they look like the backside of spoons.
Clubbing can sometimes occur without any apparent cause, and rarely the condition runs in families and is harmless.
More commonly, however, it is a sign of an underlying disorder, such as lung cancer , bronchiectasis (abnormal widening of the bronchi, the large airways in the lungs), cystic fibrosis, heart disease, liver disease, thyroid disease, stomach cancer, colon cancer, or inflammatory bowel disease.