Clinical Review
Clubbing: An update on diagnosis, differential diagnosis, pathophysiology, and clinical relevance

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Finger clubbing can be a striking physical finding. At other times, the presence of clubbing is difficult to establish by subjective examination alone and the profile angle or distal phalangeal to interphalangeal depth ratio are needed to confirm the finding. Most microscopic and imaging studies of clubbed fingers reveal hypervascularization of the distal digits. Recent research shows that when platelet precursors fail to become fragmented into platelets within the pulmonary circulation, they are easily trapped in the peripheral vasculature, releasing platelet-derived growth factor and vascular endothelial growth factor, promoters of vascularity and, ultimately, clubbing. Clinically, clubbing is associated with a number of neoplastic, pulmonary, cardiac, gastrointestinal, infectious, endocrine, psychiatric, and multisystem diseases. In narrowing the differential diagnosis, we recommend a detailed history and physical examination accompanied by focused laboratory and imaging studies. An algorithm for the evaluation of newly diagnosed clubbing is suggested.

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Clinical

Researchers have described many techniques for the accurate diagnosis of clubbing. Recognizing that the presence or absence of clubbing was not always obvious at the bedside, Lovibond43 was among the first to offer a criteria for the diagnosis of finger clubbing. Lovibond43 defined the “profile sign” of the thumb, or Lovibond's angle as it came to be known, as the angle made by the nail as it exits the proximal nailfold. He reported that a profile sign of greater than 180 degrees could be used

Differential diagnosis

Many diseases have been associated with secondary clubbing with or without HOA. Table I, Table II provide an overview.

Pathophysiology

Numerous hypotheses of the pathophysiology of clubbing have been proposed over the years. One group proposed a neurocirculatory reflex based on a patient with an ulnar artery aneurysm and subsequent ipsilateral finger clubbing.58 The authors hypothesized that clubbing is associated with local arteriovenous anastamoses provoked by alterations in vascular dynamics that allow blood to bypass capillaries; these anastamoses are actually neurohumoral end organs that allow the autonomic nervous system

Evaluation

In evaluating a patient with new-onset clubbing, it is first important to verify that the patient has true clubbing and not pseudoclubbing. Pseudoclubbing usually involves only a single digit. The digit may appear at first glance to be truly clubbed but, on closer inspection, the profile angle will likely be normal. Pseudoclubbing of a single digit can be seen in patients with a subungual tumor,68 pseudocyst,69 or osteoid osteoma.70 Generalized pseudoclubbing can be seen in disease processes

Prognosis and treatment

Clubbing has been studied widely as a prognostic factor. It has been suggested that its presence can be used to distinguish idiopathic pulmonary fibrosis from pulmonary fibrosis secondary to collagen vascular disease.77 In cystic fibrosis,78, 79 asbestosis,35 hypersensitivity pneumonitis,36 tuberculosis,80 and idiopathic pulmonary fibrosis,81 clubbing has been associated with greater severity of disease or increased risk of mortality.

The prognosis of clubbing is completely dependent on the

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      Citation Excerpt :

      If it exceeds 1, clubbing is confirmed (see Fig. 2).31 Clubbing can be congenital (associated or not with various genetic syndromes) or acquired and unilateral or bilateral.27,28 It can be isolated or occur as part of the hypertrophic osteoarthropathy syndrome, characterized by periostosis of long bones, arthralgia, and clubbing.27,28

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    Funding sources: None.

    Conflicts of interest: None identified.

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