HTT and Roifman syndrome: While a dominant mode of inheritance was highly unlikely, we investigated three high-quality variants with very rare allele frequency (<0.1%) impacting genes with a dominant mode of inheritance and shared by the two siblings (GUCY2D, HTT and RP1L1); unsurprisingly, on more detailed review, we found insufficient match to the Roifman Syndrome phenotype and only modest damaging potential (for more details see Supplementary Data 1, Supplementary Table 5 and Supplementary Note 2).