Previous studies have also been conducted on the indicators for severity of symptoms in children with POTS [17,18,19]; however, in these studies, biomarkers related to the condition of children with POTS, such as plasma Hcy, sulfur dioxide, and serum resistin, were not routinely detected, especially in the grassroots medical institutions. This evidence concerns the gene RETN and postural orthostatic tachycardia syndrome.