When stratifying the juvenile MG patients into prepubertal onset and postpubertal onset groups, we found that only prepubertal onset juvenile MG was associated with the HLA-DRB1*04:04 allele (P = 0.01), where it occurred in 26% compared to 6.4% among controls. This evidence concerns the gene HLA-DRB1 and myasthenia gravis.