<prompt> Differentia cyanosis occurs in which disease -Severe coarctationInturrupted aortic archPPHNAll of above  <response>: Ans. is d i.e., All of above Differential cyanosis -o With normally related great arteries, oxygen saturation may be higher in the upper than lower extremity in patients if there is right-to-left shunting through the ductus arteriosus. Seen with severe coarctation or interrupted aortic arch.. May also occur in patients persistent pulmonaiy hypertension of the newborn.o The differential effect is reduced if there is also right-to-left shunting at the level of the foramen ovale, or if there is left-to-right shunting across coexisting ventricular septal defect 