December 24, 2020

Finger Clubbing: Causes, Symptoms, Diagnosis and Treatment

Nail clubbing, also known as digital clubbing or just simply, clubbing, is a deformity of the finger or toe nails which occur due to the presence of a number of associated diseases, mostly diseases of the heart and lungs. In a number of cases, however, nail clubbing has been known to run in families, where it occurs without any associated disease or medical problem. It is still not clear why soft tissue in nails increase to cause nail clubbing, whether in diseases that have brought it on, or in families where different affected members have inherited it.

Synonyms: Clubbing, nail clubbing, finger clubbing, clubbed fingers, digital clubbing, watch-glass nails, drumstick fingers, Hippocratic fingers, Hippocratic nails, hypertrophic osteoarthropathy (HOA), hypertrophic pulmonary osteoarthropathy (HPOA), acropaquia.

What is finger clubbing?

Clubbing is enlargement of the tips of the fingers or toes and a change in the angle where the nails emerge. In other words, finger clubbing is the enlargement of the ends of the fingers accompanied by a downward sloping of the nails. It is called hypertrophic osteoarthropathy (HOA) if it occurs together with joint effusions (abnormal increased fluid in joints), joint pains, and abnormal skin and bone growth.

There are two forms of this disease - primary and secondary. Primary finger clubbing is simply a clubbed appearance of the fingers without any associated health problems. Secondary finger clubbing, on the other hand, describes clubbing of the finger caused by health problems affecting the organs and/or systems of the body such as lung (or pulmonary) diseases, heart (or cardiovascular) diseases, tumor (or neoplastic) diseases, infectious dieases, liver and gallbladder (or hepatobiliary) diseases, hormonal (or endocrine) diseases, and digestive (or gastrointestinal) diseases.

Finger clubbing (acropaquia)
Advanced finger clubbing. Image credit: Desherinka, CC BY-SA 4.0, via Wikimedia Commons

Clubbing itself is not harmful and does not need any treatment, but since it can be a sign of serious disease, it is important that you arrange to see your healthcare provider as soon as possible if you suspect you have it with a view to examine you and identify the cause, so that appropriate treatment can start if any underlying condition is discovered.

Finger Clubbing - Lung and Airway Disorders
Normal finger vs clubbed finger. Finger clubbing is characterized by enlarged fingertips and a loss of the normal angle at the nail bed. Note loss of angle between nail bed and the cuticle in the clubbed finger. Image credit: © Springer Science+Business Media (via MSD Manual)

What causes finger clubbing?

Although there are two forms of this condition, it is still not clear why soft tissue in nails increase to cause nail clubbing, whether in families where different affected members have inherited it (primary clubbing), or in diseases that have brought it on (secondary clubbing).

Primary clubbing is hereditary, and it is passed down through genes. Hereditary clubbing is simply a physical feature, just like the color of your eyes or your height is a physical feature. It does not signify disease. Several genes have been associated with primary clubbing, including the HPGD gene and the SLCO2A1 gene.

Secondary clubbing occurs from the effects of longstanding (or chronic) diseases, especially of the lungs and the heart, but also of a number of other chronic illnesses and chronic infections, including conditions that involve the thyroid gland or the digestive system. Although lung cancer is the most common cause of secondary clubbing (about 80%), it is also an important sign of chronic lung disease, such as cystic fibrosis and idiopathic pulmonary fibrosis.

Below are some of the disease conditions associated with secondary clubbing:
  • Lung cancer
  • Lung abscess
  • Interstitial pulmonary fibrosis (or Interstitial lung fibrosis)
  • Pulmonary tuberculosis
  • Pulmonary lymphoma
  • Congestive heart failure
  • Infective endocarditis
  • Cyanotic congenital heart disease
  • Bronchiectasis
  • Cystic fibrosis
  • Other types of cancer, including liver, gastrointestinal or Hodgkin lymphoma
  • Inflammatory bowel disease, such as Crohn's disease and Ulcerative colitis
  • Liver cirrhosis
  • Gastrointestinal neoplasms (or tumors of the gut)
  • Celiac disease
  • Ongoing severe diarrhea or dysentery
  • Graves' disease
  • An overactive thyroid gland (hyperthyroidism)

How diseases affect nail beds to cause finger clubbing

The medical conditions that cause clubbing are generally associated with decreased oxygen levels. Medical scientists believe that clubbing occurs as your body undergoes changes in response to low oxygen.

Several processes affect the nail beds in secondary clubbing. These processes lead to increase in amount of soft tissue beneath the nail beds causing nail enlargement. It is not clear why the soft tissue increases, but it may be related to inflammation and increased levels of proteins that stimulate small blood vessel growth in the nail beds.

A protein called vascular endothelial growth factor (VEGF) stimulates the growth of blood vessels, and this protein is considered a major factor in the physical changes that occur in clubbing.

What are the symptoms of finger clubbing?

Clubbing can involve your fingers and/or toes. It typically affects both hands and/or feet equally in terms of extent of deformity.

If you or your child has primary clubbing, then your fingers or toes may naturally appear large, bulging, and rounded. This will be noticeable during childhood or during the teenage years, and it will not change much over time. With primary clubbing, other family members are also likely to have finger and/or toe clubbing.

Secondary clubbing happens gradually, resulting in a change in the appearance of your fingers and/or toes. With secondary clubbing, there would be other tell-tale features of the underlying disease causing it, including signs of low oxgen in blood (or hypoxemia) called cyanosis. Cyanosis is the bluish discoloration of the lips, face, and/or nail beds due to very low oxygen in the blood (or hypoxemia) running through the arteries of the body. Tell-tale features of disease and cyanosis are not seen in primary clubbing.

Features of secondary clubbing include:
  • Softening of the nails
  • Nail beds that soften and feel spongy
  • Nails that seem to "float" instead of being firmly attached to your fingers
  • Disappearing of the angle between your nails and cuticle (see images above)
  • Enlargement or bulging of the distal portion of your finger (where your finger meets your nail - see images above)
  • Warm, red nail beds
  • Nails that curve downward and look like the bottom of the round part of a spoon (see images above)
Eventually, the nail and skin around the nail may become shiny, and the nail develops ridging.

Diagnosis of finger clubbing

Clubbing of your digits may be so subtle that you and your healthcare provider may find it difficult to identify by merely looking. However, there are a few objective criteria that are used to assess clubbing, and these help to determine whether you have developed this physical change:
  • Lovibond's profile sign: Normally, there is a sharp angle between the nail bed and the cuticle. When you have clubbing, the natural angle is lost as the nail angles down instead of up.
  • Distal/interphalangeal depth ratio: The phalanges of your finger are the sections between each bending joint. Your distal phalange, the one that includes your nail, is normally shorter depth-wise than the neighboring phalange. Clubbing is indicated when the opposite is true.
  • Schamroth window test (or Schamroth's sign): The sharp angle between your nail bed and cuticle forms a tiny diamond-shaped hole when you place your hands together with the top of your nails facing each other. When this gap disappears, it is described as Schamroth's sign (see images below).

Schamroth window test in a normal finger showing diamond-shaped window
Schamroth window test demonstrating a diamond-shaped window when fingers are not clubbed.
Image credit: BMJ Knowledge Centre

Schamroth window test in a clubbed finger demonstrating loss of diamond-shaped window
Schamroth window test demonstrating lack of window with clubbed fingers.
Image credit: BMJ Knowledge Centre

Assessing Underlying Conditions

When you start to have clubbing of your digits, your healthcare provider will evaluate you to identify any underlying disease that could be causing it. Most times, however, clubbing develops due to a chronic medical condition that was diagnosed years before the clubbing developed.

Even if you have an established lung or heart condition that is known before your finger clubbing develops, your healthcare provider may still go ahead to re-assess your condition to identify if there has been a progression in the disease that might require an adjustment to your current treatment.

Tests that you may need in the evaluation of clubbing include:
  • A physical examination to assess for signs such as weight loss, difficulty breathing, skin changes, alterations in your pulse, or altered blood pressure
  • Blood oxygen levels (or oxygen saturation) using a pulse oximeter
  • Arterial blood gas test
  • Pulmonary function tests (PFTs)
  • Chest imaging, such as chest X-ray or chest computerized tomography (CT)
  • Blood tests, including complete blood count (CBC), electrolyte levels, liver function tests (LFTs), and/or thyroid tests
  • An electrocardiogram (EKG) or echocardiogram to assess your heart function
  • Abdominal imaging, such as abdominal CT or ultrasound
  • A biopsy if there is any concerning lesion noted on any of the imaging tests

Treatment of finger clubbing

Usually, the abnormal shape and size of the digits do not cause health problems, but any underlying disease resulting in the clubbing needs to be medically and/or surgically managed, as appropriate. Treatments may prevent your clubbing from worsening and, in rare cases, can reverse some or all of the physical features of clubbing.

There are a variety of approaches used to treat the underlying cause of clubbing. Your treatment will depend on your situation. You may need management of a chronic respiratory disease, treatment of a heart disease, or interventional therapy for cancer.

Other possible treatments may include:
  • Anti-inflammatory treatment for inflammatory conditions, including some pulmonary and gastrointestinal diseases
  • Hormone replacement
  • Pacemaker implantation to improve heart function

Where do I get more information about finger clubbing?

If you notice that your fingers are clubbing or clubbed, be sure to discuss this with your healthcare provider. Clubbing can be diagnosed in your healthcare provider's office. Although clubbing itself is harmless and doesn't require treatment, it is often associated with health conditions that can worsen without treatment. And your healthcare provider is always the best source of information for the questions and concerns you may have concerning your medical problem.

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