211 Deep Phenotyping Reveals Germline Determinants of Disease Severity in Neurofibromatosis Type 2

Abstract

INTRODUCTION: Neurofibromatosis type 2 (NF2) is an autosomal dominant tumor predisposition syndrome with central and peripheral nervous system tumors and non-neoplastic manifestations including peripheral neuropathy. NF2 presents with a large variation in penetrance and severity. Although germline nonsense and frameshift NF2mutations are hypothesized to confer severe disease, the relationship between mutation type and manifestations of this disease is not completely understood. METHODS: Patients (n = 169) with NF2 (Manchester criteria) were enrolled in a Natural History protocol (NCTNCT00598351). Deep phenotypic profiles were created (serially for 5 years) including clinical evaluations, self-reported functional measures, lifetime interventions (surgical, radiation and drug treatments), and imaging (tumor number, type and volume using volumetric MRI of the neuroaxis). Validated germline mutation data (n = 68) was used to examine relationships between genotype and phenotype with attention to NF2 mutation type (indel/large deletion), genomic effect (missense/nonsense/frameshift), predicted protein effect (truncating/non-truncating) and location (exonic/intronic/splice-site). RESULTS: Tumor burden varied greatly between patients (tumor number range 1-165, median 25). We found that cranial meningiomas were a major determinant of total tumor burden. Total tumor burden (number and volume) was associated with worse KPS and decline in KPS over the study protocol (p < 0.001). We found that truncating mutations in exons 11-12 were associated with more severe disease in terms of tumor number on MRI (p = 0.0439). CONCLUSION: This is the first large scale study to deeply phenotype patients with NF2 including longitudinal analysis and demonstrates several previously unrecognized trends related to germline mutations type, imaging findings, and measures of disease severity.