Clubbing:

Hypertrophic osteoarthropathy (HOA) is characterized by clubbing of digits and, in more advanced stages, by periosteal new bone formation and synovial effusions. HOA occurs in primary and familial forms and usually begins in childhood. The secondary form of HOA is associated with intrathoracic malignancies, suppurative lung disease, congenital heart disease, and a variety of other disorders and is more common in adults. Clubbing is almost always a feature of HOA but can occur as an isolated manifestation. The presence of clubbing in isolation is generally considered to represent either an early stage or an element in the spectrum of HOA. The presence of only clubbing in a patient usually has the same clinical significance as HOA.