A schwannomatosis that causes a predisposition to develop multiple schwannoma. It is diagnosed when an individual does not meet criteria for NF2-related schwannomatosis, SMARCB1-related schwannomatosis, or LTZR1-related schwannomatosis and both of the following molecular features exist: a loss of heterozygosity (LOH) of the same chromosome 22q markers in two anatomically distinct tumors or hybrid nerve sheath tumors and a different NF2 pathogenic variant in each tumor which cannot be detected in unaffected tissue.