Pulm| Digital Clubbing

2.18 Digital Clubbing Pulmonary system review for the USMLE Step 1 Exam Digital clubbing is the enlargement of the ends of fingers and toes due to growth of connective tissue between the nail matrix and the distal portion of the digit. It is defined quantitatively as an increased angle between nail bed and nail plate (> 180°). Digital clubbing is caused by an interaction between platelets, megakaryocytes, and the growth factors platelet derived growth factor (PDGF) and vascular endothelial growth factors (VEGF). Diseases associated with digital clubbing include lung cancer, cystic fibrosis, idiopathic pulmonary fibrosis, bronchiectasis, and an empyema. Digital clubbing is usually not associated with asthma or COPD.