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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.
Signs and diagnosis
Clubbing develops in five steps:
Schamroth's test or Schamroth's window test (originally demonstrated by South African cardiologist Dr Leo Schamroth on himself) 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.
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.
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.
Clubbing is associated with:
Clubbing associated with other symptoms
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 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.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Clubbing". A list of authors is available in Wikipedia.|