In conclusion, the identification of biallelic variants in VAMP1 as a novel cause of CMS, in addition to other genes (eg, SNAP25B, SYT2) previously associated with similar presynaptic abnormalities of neuromuscular transmission,5, 6 highlights the crucial role of different SNAREs in NMJ physiology. The gene discussed is VAMP1; the disease is congenital myasthenic syndrome.