In medicine, clubbing is a deformity of the fingers and fingernails. Clubbing occurs more frequently in children born with heart defects and people with chronic heart, lung, liver, or thyroid disease. But simple hereditary clubbing can occur without underlying heart or lung problems.
Signs and symptoms
Clubbing develops in five steps:
- Fluctuation and softening of the nail bed (increased ballotability)
- Loss of the normal
- Increased convexity of the nail fold
- Thickening of the whole distal (end part of the) finger (resembling a drumstick)
- Shiny aspect and striation of the nail and skin
Schamroth’s test or Schamroth’s window test is a popular test for clubbing. When the distal phalanges (bones nearest the fingertips) of corresponding fingers of opposite hands are directly apposed (place fingernails of same finger on opposite hands against each other, nail to nail), a small diamond-shaped “window” is normally apparent between the nailbeds. If this window is obliterated, the test is positive and clubbing is present.
Diagnosis
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 and a chest CT-scan may also be performed.
Associations
Clubbing is associated with:
Lung disease:
- Lung cancer, mainly large-cell (35% of all cases), not seen frequently in small cell lung cancer
- Interstitial lung disease
- Tuberculosis
- Suppurative lung disease: lung abscess, empyema, bronchiectasis, cystic fibrosis
- Mesothelioma
- A·V fistula
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
- Hepatopulmonary syndrome, a complication of cirrhosis
- Laxative abuse
- Polyposis
- Esophageal CA
Others:
- Hyperthyroidism (thyroid acropachy)
- 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)
- Thymoma
- Thalassemia
HPOA
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 abnormalities can occasionally be found. It is known eponymously as the Touraine-Solente-Golé syndrome. This condition has been linked to mutations in the gene on the fourth chromosome (4q33-q34) coding for the enzyme 15-hydroxyprostaglandin dehydrogenase (HPGD); this leads to decreased breakdown of prostaglandin E2 and elevated levels of this substance.
Pathophysiology
The exact cause for sporadic clubbing is unknown, and there are numerous theories as to its cause. Vasodilation (distended blood vessels), secretion of growth factors (such as platelet-derived growth factor and hepatocyte growth factor) from the lungs, and other mechanisms have been proposed. The discovery of disorders in the prostaglandin metabolism in primary osteo-arthropathy has led to suggestions that overproduction of PGE2 by other tissues may be the causative factor for clubbing.
Source: Wikipedia and Health.com
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