finger clubbing
Finger clubbing is a gradual reshaping of the fingertips: the nails curve more, the soft tissue at the base of the nail swells, and the fingertip becomes broad and bulbous, sometimes likened to the end of a drumstick. It usually develops slowly over months and is painless, so people may not notice it themselves.
A simple bedside test is to place the backs of two opposite fingernails together. Normally a small diamond-shaped gap appears between them; in clubbing that gap fills in and disappears. The earliest change is a loss of the normal sharp angle where the nail meets the skin, and an abnormal sponginess of the nail bed.
The exact mechanism is not fully settled, but it is thought to involve platelet fragments and growth factors that normally would be filtered by the lungs reaching the fingertips and stimulating tissue growth. Clubbing is a clue, not a disease: in the chest it accompanies conditions such as lung cancer, bronchiectasis, lung abscess and pulmonary fibrosis, and it also occurs with certain heart, liver and bowel diseases, while some people have a harmless inherited form.
Because clubbing develops slowly and has serious associations, new clubbing — especially in a smoker — prompts a careful search for an underlying cause rather than reassurance on its own.
Clubbing is not caused by COPD or asthma alone. Finding clubbing in someone with chronic lung symptoms should redirect thinking toward cancer, suppurative lung disease or fibrosis.