In contrast, all Roifman Syndrome causal variants identified in the six cases are always compound heterozygous (Fig. 1 and Table 1), with one variant overlapping the MOPD1-implicated 5′ stem–loop critical region (U4atac snRNA positions 37, 48 and 51) or the Sm protein-binding site (U4atac snRNA position 118), while the other variant occurs at highly conserved positions in the stem II (U4atac snRNA positions 8, 13 and 16; Fig. 3). The gene discussed is RNU4ATAC; the disease is Roifman syndrome.