SNRPB and microcephaly: Genetic variants affecting the function of several core splicing factors, namely SF3B4, SF3B2, EFTUD2, SNRPB and TXNL4A, are responsible for MFD in five related but distinct syndromes known as Nager and Rodriguez syndromes (NRS), craniofacial microsomia (CFM), mandibulofacial dysostosis with microcephaly (MFDM), cerebro-costo-mandibular syndrome (CCMS) and Burn–McKeown syndrome (BMKS), respectively.