We collected detailed clinical information from five individuals with rare RNU5B-1 variants in our cohort, which revealed that the ‘RNU5B-1-related disorder’ is characterized by global developmental delay, relative macrocephaly, seizures and failure to thrive (Fig. 2d, Supplementary Tables 7 and 8 and Supplementary Note). Here, RNU5B-1 is linked to Failure to thrive.