Study of the prevalence of familial autoimmune myasthenia gravis in a Spanish cohort

•Familial autoimmune MG (FAMG) is more frequent than traditionally believed.•The FAMG phenotype is indistinguishable from the sporadic autoimmune forms of MG.•LOMG and VLOMG were the most prevalent forms in FAMG found in our cohort.•Thymoma was also associated with FAMG, but less frequently than sporadic forms.•FAMG treatment and management is the same as for sporadic MG.