FLT4 and isolated hemihyperplasia: Variants of these genes have previously been associated with the occurrence of IH (ANTXR1, FLT4, KDR) and malignancies (IGF1R), have the potential to modulate the pharmacotherapy effect of IH (ADRB2), or affect preterm birth and growth retardation (ADRB2, IGF1R), contributing more broadly to the pathogenesis of ROP.