The neurofibromatoses, including NF1, NF2, and schwannomatosis, are hereditary tumor predisposition syndromes caused by germline mutations in the NF1, NF2, and SMARCB1 tumor-suppressor genes, respectively.[1]–[4] Biallelic inactivation of these tumor-suppressor genes in susceptible cells leads to dysregulation of key cellular machinery, including activation of the Ras pathway (NF1), loss of contact-dependent inhibition of the EGFR pathway (NF2), and perturbation of the SWI-SNF chromatin remodeling complex (schwannomatosis). The gene discussed is SMARCA1; the disease is neoplasm.