Clinical and Imaging Phenotype of Schwannomatosis in Children, Adolescents and Young Adults.

Background/Objectives: To characterize the clinical and imaging phenotypes of schwannomatosis (SWN) in children, adolescents, and young adults (AYAs). Methods: This single-center retrospective cohort study included patients (age ≤ 25 years) with suspected SWN with archived magnetic resonance imaging (MRI) at Johns Hopkins between 2020-2026. Clinical characteristics, genetic testing results, and tumor imaging (including anatomic distribution), and treatment approaches were reviewed. Descriptive statistics were performed. Results: In total, thirty-eight patients with suspected SWN were identified (median age 20 years, range 6-25; 32% female). NF2-related SWN was the most common diagnosis (31/38, 82%; de novo: 24/31 (77%) and familial: 7/31 (23%)), followed by LZTR1-SWN (n = 1) and SWN-NOS/NEC (n = 2). A total of four patients (asymptomatic LZTR1 carriers (n = 2) and possible SWN (n = 2)) did not fulfill diagnostic criteria based on craniospinal and whole-body MRI. Familial NF2-SWN demonstrated a trend toward earlier presentation (median 5 vs. 8 years; p = 0.12). Visual manifestations occurred at a younger age than hearing loss (median 8 vs. 16 years; p = 0.053). Imaging burden was high (median 23 MRI/patient (range: 1-60). Bilateral vestibular schwannomas were nearly universal (30/31, 97%). Familial disease demonstrated a trend toward increased cranial meningiomas (86% vs. 54%; p = 0.20), while peripheral schwannomas (43% vs. 67%; p = 0.38) and ependymomas (14% vs. 42%; p = 0.37) were less frequent compared with de novo disease. Operative and non-operative management was documented in 65% (20/31) each. Conclusions:NF2-related SWN is the predominant subtype in a pediatric and AYA patient population and was associated with substantial early tumor burden at a tertiary specialty NF center.