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):