Any disparity between interarm BP—especially when large and persistent—should prompt consideration of diseases known to be the cause: coarctation, dissection, or aneurysm of the thoracic aorta; Takayasu (pulseless) disease; and various types of intra- and extra-arterial obstruction in an upper extremity.1,9,11,23,24 These diagnostic considerations become much more likely if the arm with the lower BP also has a grossly diminished radial pulse.