The thickening of tissues at the base of the fingernails - a sign doctors look for. It can signal serious pathology, or occasionally it is a harmless congenital abnormality.

What it's like: There is increased nail bed fluctuation. The angle between the nail and the nail bed is lost. Then, the longitudinal curvature of the nail becomes exaggerated. In extreme cases, the end of the finger looks bulbous.

Respiratory causes (and how to remember them):

• Bronchial Carcinoma (cancer in the airways)
• Mesothelioma (cancer in the pleura)
• Fibrosing Alveolitis (diffuse parenchymal lung disease)
• Bronchiectasis (pus in the airway)
• Empyema (pus in the pleura)
• Abscess (pus in the alveoli)

Cardiac causes:

• Cyanotic congenital heart disease
• Infective endocarditis

GI causes:

• Inflammatory bowel disease (crohn's or ulcerative colitis)
• Primary biliary cirrhosis