CLUBBING

Clubbing is an increase in the soft tissue under the proximal nail plate of the distal part of the fingers or toes. Its causes are varied, the mechanism unknown (1).Clubbing was first described by Hippocrates in 400 BC in an empyema patient (hence also known as hippocratic fingers) (2).

Initially, increased vascularity of the nail bed results in increased sponginess of the proximal nail plate which may be detected by compressing the nail bed and finger (1).Later, swelling of the soft tissue causes a broadening of the distal phalanx and an increase in the transverse and longitudinal curvature of the nail (3). The overlying skin stretches and takes on a polished appearance.Clubbing may be hereditary, idiopathic or acquired (3).

It may also present as unilateral  clubbing - associated with hemiplegia and vascular lesions bilateral clubbing -  associated with neoplastic, pulmonary, cardiac, gastrointestinal, infectious, endocrine, vascular and multisystemic disease (3).

The nail is pushed up, increasing the angle between the long axis of the nail and the dorsal nail fold (also known as Lovibond’s angle), which approaches 180 degrees in severe cases (3).

Clubbing may be demonstrated clinically by apposing the dorsal surfaces of two nails - the diamond shaped window seen in normal nails is abolished in the clubbed nail (Schamroth sign) (1).

Patients hardly ever notice that they have clubbing, even when it is severe. They often express surprise at their doctor's interest in such an unlikely part of their anatomy.

In case of clubbing involving a single digit, the diagnosis of pseudoclubbing should be ruled out. Causes of single digit clubbing include - Idiopathic, digital mucoid cyst, osteoid osteoma and myxochondroma (2).

Theories about the mechanism of clubbingOne theory is that clubbing is a response to arterial hypoxaemia, in which release

of an unknown humoral substance causes dilation of the vessels of the fingers and the toes. Another is that clubbing results from a neurovascular abnormality. In support of this is the fact that a vagal section may reverse clubbing.

Recent research studies have shown that platelet-derived growth factors and vascular endothelial growth factors (which are released when platelet precursors are trapped in the peripheral circulation) acts as promoters of vascularity and eventually finger clubbing (1).

However, no theory adequately explains the sheer variety of diseases in which this phenomenon occurs.

Criteria for diagnosisAll four of the features outlined below should be present before the fingernails

can be said to be clubbed:

Increased sponginess of the nail bed Loss of the usual acute angle between the nail and the nail bed Increased curvature of the nail Increased mass of the soft tissues over the terminal phalanges

Etiology by frequency Here the causes of clubbing are grouped with respect to frequency.

Common causes of clubbingCommon causes of finger clubbing can be divided up according to the system with primary

pathology:

Cardiovascular causes:

o Cyanotic congenital heart disease o Infective endocarditis

Respiratory causes: o Lung carcinoma - usually squamous cell carcinoma o pulmonary fibrosis, especially fibrosing alveolitis o cystic fibrosis o chronic pulmonary suppuration:

Bronchiectasis Empyema Lung abscess

The clubbing seen with bronchogenic carcinoma is often part of a hypertrophic osteoarthropathy.

Uncommon causes of clubbing

Uncommon causes of finger clubbing can be divided up according to the system with primary pathology:

Cardiovascular causes: o Atrial myxoma

Respiratory causes: o Tuberculosis - typically within 6 weeks of onset o Pleural mesothelioma

Gastrointestinal causes: o Liver cirrhosis o Ulcerative colitis o Crohn's disease o Coeliac disease

Endocrinological: o Thyroid acropachy in thyrotoxicosis

Rare causes of clubbingRare causes of clubbing include: Familial - usually before the age of puberty Neurodiaphragmatic tumour

Etiology by siteSites of causes of clubbing include: Cardiac Respiratory Gastrointesinal Endocrine

1. Cardiac Cardiac causes include: Cyanotic congenital heart disease Infective endocarditis Atrial myxoma

2. Respiratory Respiratory causes include: Lung carcinoma - not usually small cell carcinoma Pulmonary fibrosis, especially fibrosing alveolitis Cystic fibrosis Chronic pulmonary suppuration, e.g.:

o Bronchiectasis o Empyema o Lung abscess

Tuberculosis - typically within 6 weeks of onset Pleural mesothelioma

3. Gastrointestinal Gastrointestinal causes include

Liver cirrhosis Ulcerative colitis Crohn's disease Coeliac disease Small bowel lymphoma

4. Endocrine Endocrinological causes include:Thyrotoxicosis: in this condition clubbing is termed thyroid acropachy although this looks like clubbing and is clubbing

Unilateral clubbingUnilateral clubbing may be caused by:

Bronchial arteriovenous aneurysm Axillary artery aneurysm Idiopathic