Last reviewed 09/2021
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).