Nail clubbing, also known asdigital clubbing orclubbing, is a deformity of the finger or toenails associated with a number of diseases, anomalies and defects, some congenital, mostly of theheart andlungs.[2][3] When it occurs together withjoint effusions, joint pains, and abnormal skin and bone growth it is known ashypertrophic osteoarthropathy.[4]
Familial and hereditary clubbing and "pseudoclubbing" (people of African descent often have what appears to be clubbing)
Vascular anomalies of the affected arm such as anaxillary artery aneurysm (in unilateral clubbing)
Primary hypertrophic osteoarthropathy
Nail clubbing is not specific tochronic obstructive pulmonary disease (COPD). Therefore, in patients with COPD and significant degrees of clubbing, a search for signs of bronchogenic carcinoma (or other causes of clubbing) might still be indicated.[12] A congenital form has also been recognized.[13]
A special form of clubbing ishypertrophic pulmonary osteoarthropathy (HPOA), known in continental Europe as Pierre Marie-Bamberger syndrome. This is the combination of clubbing and thickening ofperiosteum (connective tissue lining of the bones) andsynovium (lining of joints), and is often initially diagnosed asarthritis. It is commonly associated with lung cancer.[citation needed]
Primary hypertrophic osteoarthropathy 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 enzyme15-hydroxyprostaglandin dehydrogenase (HPGD); this leads to decreased breakdown ofprostaglandin E2 and elevated levels of this substance.[14]
Overproduction of prostaglandin E2 by other tissues.[14]
Increased entry ofmegakaryocytes into the systemic circulation. Under normal circumstances in healthy individuals, megakaryocytes that arise from the bone marrow are trapped in the pulmonary capillary bed and broken down before they enter the systemic circulation. It is thought that in disorders where there is right-to-left shunting or lung malignancy, the megakaryocytes can bypass the breakdown within the pulmonary circulation and enter the systemic circulation. They are then trapped within the capillary beds within the extremities, such as the digits, and releaseplatelet-derived growth factor (PDGF) andvascular endothelial growth factor (VEGF). PDGF and VEGF have growth promoting properties and cause connective tissue hypertrophy and capillary permeability.[15]
Clubbing of the fingernail: The red line shows the outline of a clubbed nail.Schamroths window test, done to identify nail clubbing
When clubbing is observed, pseudoclubbing should be excluded before making the diagnosis. Associated conditions may be identified by taking a detailedmedical history—particular attention is paid to lung, heart, and gastrointestinal conditions—and conducting a thoroughclinical examination, which may disclose associated features relevant to the underlying diagnosis. Additional studies such as achest X-ray and a chest CT-scan may reveal otherwise asymptomatic cardiopulmonary disease.[12]
No visible clubbing – Fluctuation (increased ballotability) and softening of the nail bed only. No visible changes of nails.
Mild clubbing – Loss of the normal <165° angle (Lovibond angle) between the nailbed and the fold (cuticula). Schamroth's window (see image) is obliterated. Clubbing is not obvious at a glance.
Moderate clubbing – Increased convexity of the nail fold. Clubbing is apparent at a glance.
Gross clubbing – Thickening of the wholedistal (end part of the) finger (resembling a drumstick)
Schamroth's sign or Schamroth's window test (originally demonstrated by South African cardiologistLeo Schamroth on himself)[16] is a popular test for clubbing. When the distalphalanges (bones nearest the fingertips) of corresponding fingers of opposite hands are directlyopposed (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.
The exact frequency of clubbing in the population is not known. A 2008 study found clubbing in 1%, or 15 patients, of 1511 patients admitted to a department ofinternal medicine inBelgium. Of these, 40%, or 6 patients, turned out to have significant underlying disease of various causes, while 60%, or 9 patients, had no medical problems on further investigations and remained well over the subsequent year.[7]
^abVandemergel X, Renneboog B (July 2008). "Prevalence, aetiologies and significance of clubbing in a department of general internal medicine".Eur. J. Intern. Med.19 (5):325–329.doi:10.1016/j.ejim.2007.05.015.PMID18549933.
^abcMyers KA, Farquhar DR (2001). "The rational clinical examination: does this patient have clubbing?".JAMA.286 (3):341–347.doi:10.1001/jama.286.3.341.PMID11466101.
^Shah K, Ferrara TM, Jan A, Umair M, Irfanullah, Khan S, Ahmad W, Spritz RA (August 2017). "Homozygous SLCO2A1 translation initiation codon mutation in a Pakistani family with recessive isolated congenital nail clubbing".Br. J. Dermatol.177 (2):546–548.doi:10.1111/bjd.15094.PMID27681482.S2CID28251025.
^abUppal S, Diggle CP, Carr IM, et al. (June 2008). "Mutations in 15-hydroxyprostaglandin dehydrogenase cause primary hypertrophic osteoarthropathy".Nat. Genet.40 (6):789–793.doi:10.1038/ng.153.PMID18500342.S2CID23484059.
