Phenotypic heterogeneity in two large Roma families with a congenital myasthenic syndrome due to CHRNE 1267delG mutation. A long-term follow-up

Highlights • A description of clinical findings in 9 patients with a CMS caused by the homozygous 1267delG mutation in the AChR Ɛ subunit. • Phenotype is characterized by ophthalmoplegia, bilateral ptosis, and good response to pyridostigmine and 3,4-DAP. • Facial weakness, bulbar symptoms, neck muscle weakness, and proximal limb weakness are also observed. • A wide spectrum of phenotypes can be associated with a single mutation even in a single kinship. • The course in our cohort is moderately heterogeneous: proportion of patients with a progressive or fluctuating course is 33%.