Pragmatic Phenotype-Electrophysiology-Genomics Integration in Pediatric Congenital Myasthenic Syndromes: Insights From 36 Patients in a Single-Center Study in China.

AIMS: To characterize the clinical, electrophysiological, and genetic spectrum of pediatric CMS and evaluate genotype-informed outcomes using an integrated phenotype-electrophysiology-genomics approach. METHODS: We retrospectively reviewed 36 pediatric CMS patients evaluated at a single center between 2015 and 2025. Clinical features, RNS, targeted NGS/WES variants, ventilator use, treatments, ACMG/AMP classifications, and MG-ADL outcomes were analyzed. RESULTS: Of 36 patients, 28 (77.8%) developed symptoms in the neonatal period or infancy. Biallelic variants involved 17 CMS genes; postsynaptic CMS was most common (55.6%, 20/36). COLQ and CHRNE were the most frequent genes (13.9%, 5/36 each), followed by CHAT (11.1%, 4/36). VUS were detected in 19 patients (52.8%, 19/36), including 8 with biallelic VUS supported by phenotype, neuromuscular transmission findings, treatment response, and follow-up. RNS showed a ≥ 10% decrement in 16/21 tested patients (76.2%). CHAT-CMS was associated with higher ventilator use (3/4 vs. 6/32; p = 0.041) and early mortality (3/4 vs. 1/32; p = 0.002). Median MG-ADL improved from 5 to 3 after genotype-informed therapy. CONCLUSION: Pediatric CMS shows marked genetic heterogeneity and frequent VUS-related uncertainty. Integrating phenotype, electrophysiology, and genomics supports diagnosis and mechanism-guided therapy. CHAT-CMS is high risk for early respiratory failure and mortality.