Besides, X-linked dominant diseases seems to show a higher rate of paternal mosaicism (e.g., MECP2 and PCDH19 in Rett Syndrome and Developmental and epileptic encephalopathy 9, respectively, as shown in Table 2), however, a more thorough literature search that includes all cases using an unbiased approach is required to confirm these preliminary findings. This evidence concerns the gene PCDH19 and atypical Rett syndrome.