EFNB1 and Craniofrontonasal dysplasia: While previous studies have identified more than 140 causal variants in the EFNB1 gene, including upstream noncoding [6, 8], nonsense, missense, frameshift, splice-altering, duplication [9] and deletion [10, 11] variants, approximately 20% of CFNS patients have negative molecular testing [10, 12, 13].