An Overview of Clubbing of the Fingers

Clubbing of the fingers, also described as hypertrophic osteoarthropathy (HOA), is an enlargement of the ends of the fingers accompanied by a downward sloping of the nails. You can have primary HOA, which is simply a clubbed appearance of your fingers that is not associated with any health problems. Or you can develop secondary clubbing, which is caused by health problems such as lung cancer and heart disease.

The clubbing itself is not harmful, but since it can be a sign of disease, it is important that your medical team identifies the cause and that you are treated for your underlying condition.

Clubbing can involve your fingers and/or toes. It is typically bilateral (affecting both hands and/or feet) and it should be equal in terms of its extent on both sides.

If you or your child has primary HOA, 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 HOA, other family members are also likely to have finger and/or toe clubbing.

Secondary clubbing happens gradually, and it causes a change in the appearance of your fingers and/or toes.

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
• Enlargement or bulging of the distal portion of your finger (where your finger meets your nail)
• Warm, red nail beds
• Nails that curve downward and look like the bottom of the round part of a spoon

Eventually, the nail and skin around the nail may become shiny, and the nail develops ridging. 

Primary clubbing is hereditary, and it is passed down via genes. Hereditary clubbing is simply a physical feature, like the color of your eyes or your height. Several genes have been associated with primary clubbing, including the HPGD gene and the SLCO2A1 gene.

Secondary clubbing occurs as one of the effects of chronic lung and heart disease. Lung cancer is the most common cause of clubbing. This sign is also associated with a number of other chronic illnesses, including conditions that involve the thyroid gland or the digestive system.

There are a number of health risk factors associated with secondary clubbing, including:

• Lung cancer
• Interstitial pulmonary fibrosis
• Lung abscess
• 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
• Liver cirrhosis
• Gastrointestinal neoplasms
• Celiac disease
• Dysentery
• Graves' disease
• An overactive thyroid gland

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

Several processes affect the nail beds in secondary clubbing. The nail enlargement occurs due to the growth of excess soft tissue beneath the nail beds. The enlargement is associated with inflammation and a proliferation of small blood vessels in the nail beds.

Clubbing can be subtle, so it may be difficult for you and your medical team to verify this change in your digits.

There are a few objective criteria that are used to assess clubbing, and they can help in determining 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'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.

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

Even if you have an established lung or heart condition, your medical team will assess your condition to identify any progression that could require an adjustment of your 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
• A pulse oximeter to measure your blood oxygen level
• Pulmonary function tests (PFTs)
• Arterial blood gas test
• Chest imaging tests, 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 tests such as CT or ultrasound
• A biopsy if there is a concerning lesion noted on an imaging test

Usually, the abnormal shape and size of the digits do not cause health problems, but any underlying disease that causes 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 respiratory disease, treatment of heart disease, or interventional therapy for cancer.

Treatments may include:

• Anti-inflammatory treatment for inflammatory conditions, including some pulmonary and gastrointestinal diseases
• Hormone replacement
• Pacemaker implantation to improve heart function

If you notice that your fingers are clubbing, be sure to discuss this with your doctor. Clubbing can be diagnosed in your doctor's office. Although clubbing itself is harmless and doesn't require treatment, it is often associated with health conditions that can worsen without treatment.