CLUBBING

Definition :

Clubbing of the fingers designates the selective bulbous enlargement of the distal segments of the digits due to an increase in soft tissue.

Mechanism :

1.The circulating megakaryocytes and large platelet particles present in the venous circulation normally break up in the pulmonary vascular bed. Megakaryocyte or platelet clusters, lodged in the peripheral vasculature of the digits, release platelet-derived growth factor (PDGF) and lead to the increased vascularity, permeability, and connective tissue changes that are the hallmark of clubbing.

Release of VEGF and PDGF occurred after platelet impaction and is enhanced by hypoxia. VEGF along with PDGF induces the pathological changes of digital clubbing.

Unilateral clubbing :-

Anomalous aortic arch 
Aortic or subclavian artery aneurysm 
Pulmonary hypertension with patent ductus arteriosus 
Brachial arteriovenous aneurysm or fistula 
Recurrent shoulder dislocation 
Superior sulcus (Pancoast) tumor 

Unidigital :- 
Median nerve injury 
Sarcoidosis 

Clubbing of toes without fingers (differential clubbing) :- 
Coarctation of aorta

From LUNG INDIAMalay Sarkar¹, DM Mahesh², Irappa Madabhavi^3
1 Department of Pulmonary Medicine, Indira Gandhi Medical College, Shimla, India