Clubbing is a clinically descriptive term, referring to the bulbulous uniform swelling of soft tissues of the terminal phalynx of a digit with subsequent loss of normal angle between the nail and nail bed.

GRADES
1- The nail bed becomes soft
2- There are changes in angle of nail fold
3- The nail takes on more obvious curve
4- The end of nail becomes thick, clubbed appearance of fingertip
5- Development of shiny/ glossy change in nail and adjacent skin

CAUSES

    ◦    Idiopathic 
    ◦    Primary 
Pachydermoperiostasis
Familial clubbing
Hypertrophic osteodystrophy
 

    ◦    SECONDARY 
Pulmanory ( lung CA, cystic fibrosis, ILD, Sarcoidosis)
Cardiac ( cyanotic congenital heart disease, bacterial endocarditis)
Gastrointestinal ( crohns, ulcerative colitis)
Skin ( fischer syndrome)
Malignancies ( thyroid CA , thymoma)

What is differential clubbing?

Differential cyanosis and clubbing occurs due to the right to left shunt across the PDA.
Deoxygenated blood from the right ventricle is preferentially directed into the aorta distal to the left subclavian artery and into the lower extremities.

It is a clue to the diagnosis of Patent Ductus Arteriosus related to Eisenmenger syndrome.