Nevertheless, in support of our hypothesis is the well-documented case of digenic inheritance of Type II Usher syndrome in a subject carrying heterozygous frameshift mutations in the ADGRV1 and the PDZD7 (OMIM 612971) modifier genes [53]; additionally, cases of likely digenic inheritance involving combinations of monoallelic variants of USH1 and USH2-linked genes have been reported as well [43]. This evidence concerns the gene PDZD7 and Usher syndrome.