Kang Jin looks smaller than most of his peers. The toddler, who will soon celebrate his fourth birthday, is the size of a typical 2-year-old child. He always asks his mother to give him a piggyback or be held in her arms, because even walking a few steps tires him out.

Kang Jin suffers from breathing difficulties and poor growth, and his skin has developed a bluish color.

Kang Jin has a congenital heart defect, a condition more common than many realize. Although there is no national survey, experts estimate that for every 1,000 newborns in China, six to eight have a heart abnormality.