Clubbing

In medicine, clubbing, finger clubbing, or digital clubbing is a deformity of the fingers and fingernails that is associated with a number of diseases, mostly of the heart and lungs. Idiopathic clubbing can also occur. Hippocrates was probably the first to document clubbing as a sign of disease, and the phenomenon is therefore occasionally called Hippocratic fingers.

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Signs and diagnosis

  Clubbing develops in five steps:^[1]

1. Fluctuation and softening of the nail bed (increased ballotability)
2. Loss of the normal <165° angle ("Lovibond angle") between the nailbed and the fold (cuticula)
3. Increased convexity of the nail fold
4. Thickening of the whole distal (end part of the) finger (resembling a drumstick)
5. Shiny aspect and striation of the nail and skin

Schamroth's test or Schamroth's window test (originally demonstrated by South African cardiologist Dr Leo Schamroth on himself^[2]) is a popular test for clubbing. When the distal phalanges (bones nearest the fingertips) of corresponding fingers of opposite hands are directly apposed (placed against each other back to back), a small diamond-shaped "window" is normally apparent between the nailbeds. If this window is obliterated, the test is positive and clubbing is present.

When clubbing is encountered in patients, doctors will seek to identify its cause. They usually accomplish this by obtaining a medical history— particular attention is paid to lung, heart, and gastrointestinal conditions —and conducting a clinical examination, which may disclose associated features relevant to a diagnosis. Additional studies such as a chest x-ray may also be performed.

Pathophysiology

Even though clubbing is a widely recognized symptom of many diseases the physiological mechanism that actually causes clubbing is not well understood. Current understanding is that these diseases cause vasodilation (blood vessel dilation) in the distal circulation which leads to hypertrophy (enlarging) of the tissue of the nailbeds and thus to the clubbed fingernails.

Other factors that have been implicated are the local effects of growth factors (such as platelet-derived growth factor and hepatocyte growth factor) that are usually confined to the pulmonary capillary bed. Many of the conditions associated with clubbing result in shunting across some of the capillary beds in the pulmonary circulation.

Disease associations

Although many diseases are associated with clubbing (particularly lung diseases), the reports are fairly anecdotal. Prospective studies of patients presenting with clubbing have not yet been performed, and hence there is no conclusive evidence of these associations.

Isolated clubbing

  Clubbing is associated with:

• Lung disease:
  • Lung cancer, mainly large-cell (35% of all cases), not seen frequently in small cell lung cancer^[3]
  • Interstitial lung disease
  • Tuberculosis
  • Bronchiectasis
  • Suppurative lung disease: lung abscess, empyema
  • Cystic fibrosis
  • Pulmonary hypertension
  • Mesothelioma
  • It is worth noting that clubbing is not associated with chronic obstructive pulmonary disease (COPD). Indeed, the presence of clubbing in a patient with COPD should prompt a search for an underlying (lung) cancer.
• Heart disease:
  • Any disease featuring chronic hypoxia
  • Congenital cyanotic heart disease (most common cardiac cause)
  • Subacute bacterial endocarditis
  • Atrial myxoma (benign tumor)
• Gastrointestinal and hepatobiliary:
  • Malabsorption
  • Crohn's disease and ulcerative colitis
  • Cirrhosis, especially in primary biliary cirrhosis^[4]
  • Other liver diseases (in the "hepatopulmonary syndrome", a complication of cirrhosis)^[5]

• Others:
  • Hyperthyroidism (thyroid acropachy)^[6]
  • Familial and racial clubbing and "pseudoclubbing" (people of African descent often have what appears to be clubbing)
  • Vascular anomalies of the affected arm such as an axillary artery aneurysm (in unilateral clubbing)

Clubbing associated with other symptoms

HPOA

Main article: Periosteal reaction

  A special form of clubbing is hypertrophic pulmonary osteo-arthropathy, known in continental Europe as Pierre Marie-Bamberger syndrome. (In dogs the condition is known as hypertrophic osteopathy.) This is the combination of clubbing and thickening of periosteum (connective tissue lining of the bones) and synovium (lining of joints), and is often initially diagnosed as arthritis. It is commonly associated with lung cancer.

Primary HOA

Primary hypertrophic osteo-arthropathy is HPOA without signs of pulmonary disease. This form has a hereditary component, although subtle cardiac abnormalties can occasionally be found. It is known in continental Europe as the Touraine-Solente-Golé syndrome.

See also

• Periosteal reaction for more on HPOA and primary HOA
• Genetic clubbed thumb

References

1. ^ Myers KA, Farquhar DR. The rational clinical examination: does this patient have clubbing? JAMA. 2001;286:341-7. PMID 11466101.
2. ^ Schamroth L. Personal experience. S Afr Med J 1976;50:297-300. PMID 1265563.
3. ^ Sridhar KS, Lobo CF, Altman RD. Digital clubbing and lung cancer. Chest 1998;114:1535-37. PMID 9872183
4. ^ Epstein O, Dick R, Sherlock S (1981). "Prospective study of periostitis and finger clubbing in primary biliary cirrhosis and other forms of chronic liver disease". Gut 22 (3): 203-6. PMID 7227854.
5. ^ Naeije R. Hepatopulmonary syndrome and portopulmonary hypertension. Swiss Med Wkly. 2003;133:163-9. PMID 12715285.
6. ^ -724565997 at GPnotebook