Introduction: Congenital myasthenic syndromes (CMS) are rare, genetically heterogeneous disorders caused by pathogenic variants affecting proteins of the neuromuscular junction, leading to impaired neuromuscular transmission. We present three pediatric cases with distinct mutations, with overlapping phenotypes and response to salbutamol. Case presentation: Case 1: A 6-year-old girl presented with gross motor development delay , proximal weakness, ptosis and fatiguability . Nerve conduction studies with repetitive nerve stimulation are normal. Whole-exome sequencing identified compound homozygous pathogenic variants in the CHRNE gene Case 2: A 4.5-year-old born to consanguineous parents, with a similar presentation to Case 1. Additionally , he had a history of bilateral vocal cord palsy requiring tracheostomy for 2.5 years.Whole-exome sequencing identified a homozygous likely pathogenic mutation in the AGRN gene. Case 3: A 10-year-old boy with kyphoscoliosis and severe respiratory tract infection, with symptoms similar to case 1. His muscle biopsy suggested myopathy . Whole-exome sequencing identified compound heterozygous pathogenic variants in the DOK7 gene. Conclusion: CMS should be suspected in patients presented with early onset weakness, especially associated with ptosis and fatiguability . A high index of suspicion is needed as routine tests such as Nerve conduction study and muscle biopsy could be misleading. Genetic testing is important for precise management, as the therapeutic agent depends on the genetic mutation.