Isolated Growth Hormone Deficiency type 1 (IGHD1; [46]) is caused by mutations in the RNPC3 gene coding for the U11/U12-65K protein, and Myelodysplastic Syndrome (MDS; [47]) by somatic mutations in the ZRSR2 gene coding for Urp protein involved in 3′ splice site (3′ss) recognition [48]. Here, ZRSR2 is linked to hyperinsulinemic hypoglycemia, familial, 4.