CTLA4 and myasthenia gravis: MG has a genetic association to HLA-DR3 or ancestral haplotype 8.1 in early-onset MG (MG onset before age 50 years) with thymic hyperplasia and several weaker associations to polymorphisms in immunoregulatory genes such as FcγR, TNF-α/β, GM-phenotypes, CTLA-4 [10], HLA, and PTPN22∗R620W [11].