Clubbing is a thickening of the flesh under toe and finger nails. The nail curves downward, instead of lying flat.

Clubbing is associated with a wide number of diseases. It is most often noted in heart and lung diseases that cause decreased blood oxygen and blue skin (cyanosis).

Clubbing may also be due to lung lung cancer, and diseases of the liver and the gastrointestinal tract.

Clubbing may also occur in families. In this case it may not be due to an underlying disease.

• Congenital heart disease (cyanotic type)
  • Tetralogy of Fallot
  • Tricuspid atresia
  • Transposition of the great vessels
  • Total anomalous venous return
  • Truncus arteriosus
• Cystic fibrosis
• Bronchiectasis
• Lung abscess
• Crohn's disease
• Celiac disease
• Cirrhosis
• Lung cancer
• Pulmonary fibrosis

There is no specific treatment for the clubbing itself. Home care depends on the specific diagnosis.

If you notice clubbing, call your health care provider.

A person with clubbing generally has other symptoms and signs that define a specific condition. Diagnosis of that condition is based on family history, medical history, and a physical exam that looks at the lungs and chest. 

Medical history questions may include:

• When did you first notice this?
• Does it affect the fingers, toes, or both?
• Has it been becoming more noticeable?
• What other symptoms are also present?
• Is there any breathing difficulty?
• Is the skin ever bluish colored?

The following tests may be done:

• Chest x-ray
• Chest CT scan
• EKG
• Echocardiogram
• Arterial blood gas
• Pulmonary function tests

Zipes DP, Libby P, Bonow RO, Braunwald E, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed. St. Louis, Mo; WB Saunders; 2005:78-79.

Murray J, Nadel J. Textbook of Respiratory Medicine. 3rd ed. Philadelphia, Pa: WB Saunders; 2000:506. 

Spicknall KE. Clubbing: an update on diagnosis, differential diagnosis, pathophysiology, and clinical relevance. J Am Acad Dermatol. 2005; 52(6): 1020-8