For a majority of these, no identifiable recognized genetic condition or related constitutional gene variant was found; however, as well as for the NF1 gene in neurofibromatosis, there are now known to be several genes in which mutations can underlie NF2 or schwannomatosis, including SMARCB1, LZTR1, or NF2 genes [27], and not all of the cases which had genetic analysis may have been tested for all relevant genes. This evidence concerns the gene NF2 and neurofibromatosis.