Sudden Clubbing of the Fingers or Toes: Beware of Lung Cancer

When the fingertips (or toe tips) become enlarged and deformed, making the entire finger or toe look bulbous like a wooden mallet, this abnormal appearance has a medical term called clubbing of the fingers (or toes), also known as drumstick fingers. It is a sign of many serious diseases, including lung cancer.

There is a simple self-test for clubbing: place the nail beds of the corresponding fingers of both hands together (thumb to thumb, index finger to index finger). If there is a clear gap between them, it is not clubbing; if there is no gap, it is clubbing. Many people today have slightly deformed fingers from long-term keyboard use, but this deformation is fundamentally different from clubbing.

Clubbing results from tissue hypoxia leading to hyperplasia and thickening of the distal phalanges, which become club-shaped. Its characteristic features are obvious widening and thickening of the distal phalanx, with the nail arching upward from root to tip, so that the angle between the dorsal skin of the digit and the nail base equals or exceeds 180°. If the two nail beds are placed together and a gap with a curved shape remains between them, this indicates that the base angle is less than 180°; therefore this simple method can be used to rule out clubbing.

Clubbing of the fingers (or toes) is seen in many diseases; many lung cancer patients have clubbing. However, lung cancer is not the only disease that causes it. Cyanotic congenital heart disease such as tetralogy of Fallot, total anomalous pulmonary venous drainage, pulmonary arteriovenous aneurysm, subacute bacterial endocarditis, infective myocarditis, rheumatic heart disease, chronic congestive heart failure, and pericarditis can also produce clubbing. In the respiratory system, besides lung cancer, bronchiectasis, chronic lung abscess, emphysema, pulmonary tuberculosis, and empyema can also lead to clubbing. Of course, the lung diseases most commonly associated with clubbing remain lung cancer, chronic septic pulmonary disease, and intrapulmonary shunts. Many intestinal diseases also cause clubbing, such as Crohn's disease, chronic ulcerative colitis, intestinal tuberculosis, chronic bacillary dysentery, amoebic dysentery, ascariasis, multiple colonic polyps, and malabsorption syndrome. Clubbing is also one of the clinical signs of liver cirrhosis. In addition, idiopathic osteoarthropathy, syringomyelia, congenital syphilis, and arsenic, phosphorus, and alcohol poisoning can also produce clubbing.

Therefore clubbing is a signal that warrants attention, but it cannot by itself diagnose any particular disease. Once clubbing appears, other symptoms must be considered to judge the possible causes, and relevant examinations must be performed to determine what disease the patient has. Lung disease patients mostly have respiratory symptoms such as cough, chest pain, and chest tightness, and often a long smoking history; intestinal disease patients have indigestion, diarrhea, or constipation; heart disease patients mostly present with cyanosis; liver cirrhosis patients have accompanying symptoms such as discomfort or pain in the liver area and a dull, dark complexion; osteoarticular disease not only produces clubbing but also other bone and joint symptoms; syphilis patients usually also have skin lesions, hard chancre, and inguinal lymphadenopathy; poisoning patients mostly present with acute or chronic poisoning symptoms. All of these diseases can be confirmed by further examination.