On the basis of their atypical phenotypes (Supplementary Table S1), this demonstrates that mutations on the non-deleted chromosome can lead to unmasking of autosomal recessive conditions such as cerebral dysgenesis, neuropathy, ichthyosis and keratoderma, Kousseff, and a potentially autosomal recessive form of Opitz G/BBB syndrome.11 Notably only two genes with embryonic lethality in mice show low mutation load in this cohort: HIRA and PI4KA (Tables 1 and 2, Figure 3). This evidence concerns the gene PI4KA and Opitz G/BBB syndrome.