While schwannomatosis is a genetic condition, it does not have a clear pattern of inheritance like NF1 and NF2. Also, unlike NF1 and NF2, people may carry a schwannomatosis gene change but not ever develop symptoms.

In some families, more than one person has been diagnosed with schwannomatosis. This is called familial schwannomatosis. In other families, only one person may be diagnosed with schwannomatosis. This is called sporadic schwannomatosis. Some people have features of schwannomatosis that are limited to only one part of their body. This is called mosaic schwannomatosis or segmental schwannomatosis.

A gene called INI1 (also called SMARCB1) was identified in 2007 as one of the genes that can cause schwannomatosis. However, for many people with schwannomatosis, the INI1 gene is not the cause of their condition. It is thought that a little less than half of people with familial schwannomatosis have an INI1 mutation causing their symptoms and that only about 7-10% of people with sporadic schwannomatosis have an INI1 mutation. As yet, there have been no other genes found to cause schwannomatosis.