Nail clubbing, also known as digital clubbing or clubbing, is a deformity of the finger or toe
nails associated with a number of diseases, mostly of the
heart and
lungs.[2][3] When it occurs together with
joint effusions, joint pains, and abnormal skin and bone growth it is known as
hypertrophic osteoarthropathy.[4]
The incidence of clubbing is unknown; it was present in about 1% of people admitted to an
internal medicine unit of a hospital.[5] Clubbing has been recognized as a sign of disease since the time of
Hippocrates.[5]
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 an
axillary artery aneurysm (in unilateral clubbing)
Nail clubbing is not specific to
chronic 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 is
hypertrophic pulmonary osteoarthropathy (HPOA), known in continental Europe as Pierre Marie-Bamberger syndrome. 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.[citation needed]
Primary hypertrophic osteoarthropathy
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 enzyme
15-hydroxyprostaglandin dehydrogenase (HPGD); this leads to decreased breakdown of
prostaglandin E2 and elevated levels of this substance.[14]
Pathogenesis
The exact cause for sporadic clubbing is unknown. Theories as to its cause include:
Overproduction of prostaglandin E2 by other tissues.[14]
Increased entry of
megakaryocytes 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 release
platelet-derived growth factor (PDGF) and
vascular endothelial growth factor (VEGF). PDGF and VEGF have growth promoting properties and cause connective tissue hypertrophy and capillary permeability.[15]
Diagnosis
When clubbing is observed, pseudoclubbing[further explanation needed] should be excluded before making the diagnosis. Associated conditions may be identified by taking a detailed
medical history—particular attention is paid to lung, heart, and gastrointestinal conditions—and conducting a thorough
clinical examination, which may disclose associated features relevant to the underlying diagnosis. Additional studies such as a
chest 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 below) 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 whole
distal (end part of the) finger (resembling a drumstick)
Schamroth's sign or Schamroth's window test (originally demonstrated by South African cardiologist
Leo Schamroth on himself)[16] is a popular test for clubbing. When the distal
phalanges (bones nearest the fingertips) of corresponding fingers of opposite hands are directly
opposed (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.
Severe clubbing
Front view
Side views
Cyanotic nail beds
Epidemiology
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 of
internal medicine in
Belgium. 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]
History
At least since the time of
Hippocrates, clubbing has been recognized as a sign of disease.[5] The phenomenon has been called "Hippocratic fingers".
The Dutch painter
Dick Ket had nail clubbing as is seen from his paintings. He had an underlying disease, probably
dextrocardia.[17]
^
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): 325–9.
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): 341–7.
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): 789–93.
doi:
10.1038/ng.153.
PMID18500342.
S2CID23484059.