POLR1B and Treacher-Collins syndrome: TCS is characterized by downslanting palpebral fissures, facial bone hypoplasia, micrognathia and external ear anomalies including microtia in addition to conductive hearing loss.35–37 Some individuals with TCS may also have a cleft palate or choanal atresia.37 Although TCS is most frequently attributed to heterozygous pathogenic variants in TCOF1, rarer forms of this condition result from heterozygous pathogenic variant in POLR1B or POLR1D, or biallelic pathogenic variants in POLR1C or POLR1D.