In finger clubbing, the tissues at the base of the nail are thickened and the angle between the nail base and the adjacent skin on the finger (this should measure approximately 160 degrees – figure 18a,b) becomes obliterated. Application of light pressure at the base of the nail is associated with excessive movement of the nail bed. In clubbing, the nail looses its longitudinal curve and becomes convex from above downwards as well as from side to side. In the late stages, there may be associated swelling of the tips of the fingers. Hypertrophic pulmonary osteoarthropathy may be associated with clubbing in bronchial carcinoma; involvement of the wrist joints can be looked for at this stage.
Clubbing may also involve the toes, particularly the congenital variety. Common causes of clubbing are carcinoma and purulent conditions of the lung (bronchiectasis, lung abscess, empyema), congenital heart disease and infective endocarditis. Less common conditions are pulmonary fibrosis, fibrosing alveolitis, pulmonary tuberculosis, pleural mesothelioma, cystic fibrosis, celiac and inflammatory bowel disease, cirrhosis, malabsorption, thyrotoxicosis and bronchial arteriovenous malformations.