Clubbed nails were described in ancient times by Hippocrates and is a clinical sign that may accompany a number of different disease processes. Clubbing refers to swelling in the tip of the digit that results in loss of the normal angle seen between the nail and the nail bed. The fingertips appear broader and rounder when clubbing is present. While the exact mechanism that leads to clubbing is poorly understood, it is known to develop most often in people with conditions of the heart or lungs that decrease the total amount of oxygen in the blood. However, clubbing can also accompany malignancies and some gastrointestinal conditions. Clubbing may have a slow onset to the point where the individual is unaware of the change. It is usually painless but can rarely be accompanied by discomfort in the fingertips. Rare skin conditions including pachydermoperiostosis and palmoplantar keratoderma are unusual causes of nail clubbing.

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