RNU4ATAC and Roifman syndrome: Using whole-genome sequencing of two affected siblings and targeted Sanger sequencing of four unrelated families, we have demonstrated that Roifman Syndrome is caused by compound heterozygous single-nucleotide variants (SNVs) in the minor spliceosomal snRNA gene RNU4ATAC, which was already implicated in a distinct and severe congenital disorder, MOPD1.