A broadening and thickening of the fingers or toes (distal phalanx) with increased lengthwise curvature and curvature of the tip of the nail, with flattening of the angle between the cuticle and nail. Clubbing is associated with a wide number of diseases, although it is most often noted in diseases of the heart and lungs that cause decreased blood oxygen and skin blueness (cyanosis) or lung cancer. Clubbing can also be associated with other diseases such as diseases of the liver and the gastrointestinal tract. It may also occur in families without signifying an underlying disease.