How to Cite This Chapter: Chaudhry S, Goncerz G. Clubbing. McMaster Textbook of Internal Medicine. Kraków: Medycyna Praktyczna. Accessed July 18, 2024.
Last Updated: April 2, 2022
Last Reviewed: April 2, 2022
Chapter Information

Etiology and PathogenesisTop

Clubbing of the fingers (with their shape resembling drumsticks) develops due to the proliferation of the connective tissue of the dorsal aspect of distal phalanges of the fingers or less frequently of the toes, which leads to elevation of the nail (see Figure 6 in Fingers in Rheumatic Diseases). Periungual erythema is commonly present. The angle between the nail bed and the nail fold is ≥180 degrees (a normal angle is ~160 degrees). The underlying mechanism of clubbing is unknown; however, growth factors such as vascular endothelial growth factor (VEGF), growth hormone, and platelet-derived growth factor (PDGF) seem to play a role along with hypoxia in certain diseases.


1) Pulmonary: Pulmonary neoplasms (non–small cell lung cancer, mesothelioma, adenocarcinoma), pulmonary fibrosis, subacute or chronic inflammatory or infectious conditions (eg, empyema, lung abscesses, bronchiectasis, tuberculosis), cystic fibrosis, sarcoidosis.

2) Cardiac: Congenital cyanotic heart disease, infective endocarditis, left atrial myxoma.

3) Gastrointestinal: Crohn disease, ulcerative colitis, cirrhosis (biliary and portal).

4) Endocrine: Graves disease, thyrotoxicosis.

5) Vascular: Arteriovenous fistulas or aneurysm (classically unilateral clubbing).

6) Idiopathic clubbing.

Bilateral clubbing is characteristic for central cyanosis. Clubbing limited to one limb is a result of impaired arterial perfusion in the affected limb due to patent ductus arteriosus, aneurysm (eg, of the aorta or subclavian artery), arteriovenous fistula (in patients treated with hemodialysis), or arteritis. It may also occur in the course of hypertrophic osteodystrophy (painful subperiosteal formation of new bone), which is additionally characterized by periosteal thickening palpable over surfaces of the bones not covered by muscles (around the ankles and wrists) and tenderness in these locations, as well as edema, joint pain, and features of joint effusion (most frequently affecting the knees, ankles, and elbows). In primary hypertrophic osteodystrophy generalized cutaneous thickening may occur, with the skin becoming folded. The most frequent (>90%) cause of secondary hypertrophic osteodystrophy is paraneoplastic, occurring in lung cancer, commonly known as hypertrophic pulmonary osteoarthropathy (HPOA). However, other pulmonary infections, cystic fibrosis, right to left cardiac shunting, lymphomas, and especially pleural neoplasms have also been associated with HPOA.


A detailed history and physical examination are required to identify the underlying etiology. Further diagnostic workup should be performed depending on the suspected organ system involved (etiology: see Etiology and Pathogenesis, above).

If HPOA is suspected, radiographs of the epiphysis of long bones (revealing periosteal thickening) can be obtained. Bone scintigraphy can be helpful in excluding skeletal involvement. Because of the association of this disorder with pulmonary malignancies, chest radiographs and computed tomography (CT) may be necessary.

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