Absence of the Diamond-Shaped Window
The physical gap between the nail beds disappears entirely due to the convex rounding and swelling of the distal fingertips.
Description
The patient is asked to place the fingernails of their index fingers together, pointing downwards, to see if a small diamond-shaped gap appears. This simple observational technique, popularized by Dr. Leo Schamroth, detects the loss of the normal nail bed angle. It provides a visual clue of chronic hypoxia and vascular changes often driven by pulmonary tumors.