POLR1D and Treacher-Collins syndrome: The literature describes four clinical subtypes: Treacher Collins syndromes 1: TCS1 is caused by pathogenic variants of the TCOF1 gene; Treacher Collins syndromes 2: TCS2 is caused by pathogenic variants in the POLR1D gene; and Treacher Collins syndromes 3: TCS3 caused by pathogenic variants in the POLR1C gene and lately identified POLR1B gene as a new gene responsible for a novel Treacher Collins syndromes 4: TCS4 [6] (Table 1).