Congenital myasthenic syndromes comprise clinically and genetically heterogeneous disorders resulting from presynaptic, synaptic, or postsynaptic defects. Mutations in the COLQ gene result in acetylcholinesterase deficiency and cause a rare, autosomal recessive synaptic form of congenital myasthenic syndrome, with variable age of onset and clinical severity. We present four unrelated patients with a homozygous W148X mutation in the COLQ gene. Signs began at birth in all, but subsequent severity ranged from independent ambulation to wheelchair use during childhood. Treatment was partly effective; one patient was asymptomatic with 3,4-diaminopyridine treatment. These cases illustrate the clinical features and treatment results associated with this particular genotype, which appears to be relatively frequent among Turkish patients with congenital myasthenic syndrome.