Have you noticed changes in the shape of your fingernails and tips of fingers? Have they become rounded and spongy?
This is called clubbing and can be a sign of various diseases.
What exactly is fingernail clubbing?
Simply put, fingernail, digital clubbing, or acropachy, is rounding of fingernails and enlargement of ends of fingers and/or toes. It is an important, yet unspecific clinical sign, as it can be seen in various diseases of different systems of organs.
Normally, the angle at which the skin meets the nail at its root is obtuse, so the upper surface of a fingertip is slightly concave. In clubbing, this angle tends to flatten, and the upper fingertip surface becomes flat or even rounded and convex.
Do I have clubbing?
It is simple to check this: put the tips of your thumbs next to each other, nail to a nail, joint to a joint. You should be able to see a small diamond-shaped space between them. If you can’t, you probably have fingernail clubbing. Fun fact: this is called Schamroth’s sign, named after the doctor who first described it and used it to diagnose himself with endocarditis.
There is another sign of clubbing: press the base of a nail. It is normally very close to the bone underneath it, and it won’t move. If it does, if it feels elastic and spongy, it is one more sign that something’s not right.
How does clubbing develop?
Although this unusual shape of fingers and nails was first described in the fifth century B.C. by Hippocrates, the father of medicine himself, to the present day the exact mechanism of how clubbing develops remains unclear. What connects the variety of diseases associated with clubbing are high levels of substances known as vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) in the blood, and they are nowadays usually considered to be the main culprits for clubbing.
However, it is important to mention that one could have a naturally curved shape of nails and/or fingers, without it being a reason for concern. In this case, they would be having it since birth. If your fingers or fingernails have changed shape in the past few months or years and you suspect something is going on, do seek medical attention.
Meanwhile, let’s take a look at the diseases and conditions that can be associated with clubbing.
What can cause clubbing?
- Lung diseases
Lung diseases are the cause of clubbing in roughly 75-80% of cases, the most common and worrisome among them being lung cancer. Clubbing in this case is a part of the so-called paraneoplastic syndrome, and it is symmetrical and progressive. Other symptoms, include persistent cough without a known reason, blood in the sputum, chest pain, shortness of breath, weakness, or loss of weight.
When it comes to non-malignant diseases, the main cause of clubbing is chronic lung infections such as chronic empyema, pneumonitis, lung abscesses, actinomycosis, or pneumoconiosis. Diseases such as idiopathicbronchiectasis and cystic fibrosis should be mentioned here too, both as a potential cause of clubbing and a facilitating factor for the development of the previously mentioned chronic infections. Pulmonary fibrosis is a potential cause of clubbing too.
- Cardiovascular diseases
Cardiovascular diseases are the second most common cause of finger clubbing. Clubbing is usually associated with inherited anomalies, including cyanotic congenital heart diseases (the most common is tetralogy of Fallot) and pulmonaryarteriovenous fistula. More rarely, clubbing can be caused by bacterial endocarditis (remember Dr. Schamroth?), chronic heart failure, or heart tumors such as atrial myxoma.
- Inflammatory bowel diseases (IBDs)
Clubbing can also be a sign of inflammatory bowel disease: Crohn’s disease or ulcerous colitis. In general, more often present in those with Crohn’s disease, and in those with an active rather than an inactive IBD. It is reported that up to one-third of patients with an IBD have clubbing, or another rheumatologic manifestation of the disease, arthritis for example.
Clubbing can hardly be the first sign of such a disease that would be used to make a suspicion or a diagnosis. Other symptoms such as abdominal pain, frequent diarrheas, fatigue, and weight loss are present from the very onset of the disease and the ones to build a diagnosis with.
However, clubbing is not a negligible symptom in an IBD as it suggests a more severe disease and a poor prognosis.
Finger clubbing is a well-known sign of chronic liver disease. It is most often present in primary biliary cirrhosis and chronic active hepatitis, but can also be seen in alcoholic cirrhosis, portal cirrhosis, biliary atresia, or hepatic amyloidosis.
Cirrhosis is scarring (fibrosis) of the liver, present in the late stages of different chronic liver diseases. Apart from clubbing, symptoms include jaundice, fatigue, weight loss, itchy skin, loss of appetite, bruising, swelling, hand redness, etc. Cirrhosis is not curable, but its progress can be slowed down with certain medications.
Transplantation is the only potential solution to the problem. A 1981 study by Huaux and associates reported abatement of finger clubbing related to cirrhosis after successful liver transplantation
- Other conditions
There are some other conditions that may infrequently cause finger clubbing. Some of them include:
- Celiac disease
- Chronic myelocytic leukemia
- Renal carcinoma
- Secondary polycythemia
- Exposure to mercury, arsenic, beryllium, phosphorus, etc.
Clubbing on only one extremity can suggest a localized vascular disease, such as anomalies or aneurysms of individual blood vessels.
Clubbing of toes without clubbing of fingers, especially if associated with better muscularity of the upper body, suggests coarctation of the aorta.
How is clubbing treated?
Clubbing itself is not treated, but the underlying condition. Treatment options vary depending on the nature of the disease that caused fingernail clubbing.
It is reported that, once the appropriate therapy for the primary disease is started, clubbing may reduce or disappear, but data on the prognosis of clubbing is very scarce.
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