DefinitionClubbing is a thickening of the flesh under the toenails and fingernails. The nail curves downward, similar to the shape of the round part of an upside-down spoon.Alternative NamesClubbingConsiderationsClubbing occurs with a wide number of diseases. It is most often found in heart and lung diseases that cause a lower-than-normal amount of oxygen in the blood.Clubbing may also be due to lung cancer, and diseases of the liver and gastrointestinal tract.Clubbing may also occur in families. In this case it may not be due to an underlying disease.Common CausesChronic lung conditions BronchiectasisCystic fibrosisLung abscessLung cancerPulmonary fibrosisCongenital Heart disease (cyanotic type) Tetralogy of FallotTotal anomalous venous returnTransposition of the great vesselsTricuspid at