Clubbing of Fingertips
Definition and Physical Characteristics
Clubbing is a focal enlargement of the connective tissue in the terminal phalanges that changes the shape of nails, making them abnormally curved and shiny, with a characteristic bulbous appearance of the distal digit. 1
Key Diagnostic Features
Loss of the hyponychial angle (the normal angle between the nail bed and nail fold disappears) due to increased vascularity in the nail bed leading to hyperplasia of fibrous tissue and edema 1
Objective measurement: The distal phalangeal depth (DPD) at the nail base divided by the interphalangeal depth (IPD) yields a ratio >1 in clubbing, whereas normal fingers have a DPD/IPD ratio <1 1
Profile angle measurement can confirm clubbing when subjective examination is difficult to interpret 2
The nail bed becomes fluctuant on palpation due to underlying tissue changes 1
Pathophysiology
Hypervascularization of the distal digits is the consistent microscopic and imaging finding in clubbed fingers 2
In hypoxic conditions with extrapulmonary shunting, large megakaryocyte fragments fail to fragment into platelets within the pulmonary circulation and instead impact at the most distal sites, releasing platelet-derived growth factor and vascular endothelial growth factor (VEGF) 3
VEGF appears central to clubbing development, producing vascular hyperplasia, edema, and fibroblast/osteoblast proliferation—the exact histologic characteristics of clubbing 3
Enhanced platelet/endothelial cell activation is common to the many internal illnesses associated with digital clubbing 3
Associated Conditions
Pulmonary Causes (Most Common)
Clubbing is associated with neoplastic, pulmonary, cardiac, gastrointestinal, infectious, endocrine, psychiatric, and multisystem diseases 2
Pulmonary arteriovenous malformations create right-to-left shunt physiology presenting as dyspnea, cyanosis, and clubbing 1
In lung cancer, growth factors may gain direct entrance to systemic circulation 3
Non-Pulmonary Systemic Diseases
22% of clubbing patients have chronic liver disease, 17% have hypothyroidism, 8% have HIV infection, and 5% have Graves' disease/hyperthyroidism 4
Over one-third of patients with nail clubbing have non-pulmonary systemic disease, with males having decreased odds of concurrent respiratory disease (OR 0.37,95% CI 0.14-0.92) 4
Hereditary hemorrhagic telangiectasia with juvenile polyposis syndrome can present with digital clubbing as the only physical finding 1
Primary Form
Touraine-Solente-Gole syndrome (primary hypertrophic osteoarthropathy) presents with clubbing mostly associated with bone pain, hyperhydrosis, pachydermy, and forehead wrinkling 5
When clubbing is associated with other diseases, it is called Bamberger-Pierre-Marie syndrome (secondary hypertrophic osteoarthropathy) 5
Clinical Evaluation Algorithm
Obtain detailed history focusing on: respiratory symptoms (dyspnea, cyanosis), gastrointestinal symptoms (bleeding, diarrhea), cardiac symptoms, and family history of similar findings 2
Perform focused physical examination looking for: telangiectasias, cyanosis, signs of liver disease, thyroid abnormalities, and cardiac murmurs 2, 1
Order focused laboratory studies based on clinical suspicion: complete blood count, liver function tests, thyroid function tests, HIV testing if risk factors present 4
Obtain imaging studies as indicated: chest radiograph or CT for pulmonary evaluation, echocardiography for cardiac shunts, abdominal imaging for liver disease 2
Important Clinical Pearls
Clubbing is potentially reversible if the underlying condition is cured—embolization of pulmonary AVMs can resolve systemic symptoms, though severe long-standing clubbing may persist 1
Do not assume pulmonary disease is the cause without thorough evaluation, as more than one-third of cases have non-pulmonary etiologies 4
The presence of clubbing without cutaneous telangiectasias does not exclude hereditary hemorrhagic telangiectasia, particularly when pulmonary AVMs are present 1
Male patients with clubbing are less likely to have respiratory disease as the underlying cause compared to females 4