What condition causes infants to appear deep red to purplish with crying?

The condition that causes infants to appear deep red to purplish with crying is polycythemia. This condition is characterized by an increased concentration of red blood cells in the bloodstream. When an infant with polycythemia cries, the elevated red blood cell mass can lead to a noticeable change in skin color, making the skin appear more red or purplish. This phenomenon occurs due to the significantly greater volume of red blood cells that enhance the redness of the skin, particularly in areas with high blood flow such as the face.

In contrast, respiratory distress syndrome primarily affects the respiratory function and does not typically alter skin color in this manner. Jaundice results from an accumulation of bilirubin in the blood, which usually manifests as a yellowing of the skin and eyes, not a reddening. Dehydration can cause dry skin and other signs of insufficient fluid intake, but it does not typically result in the deep red or purplish hue associated with polycythemia during periods of crying. Understanding the pathophysiology of these conditions helps in recognizing the signs and symptoms that delineate them from one another, making polycythemia the correct choice in this scenario.