Estrada et al.58 suggested that the C4 deletions could be the functional driver of the NMO association and call the attention that the same C4 CNV and DRB1*03:01–DQA1*05:01/3/5–DQB1*02:01 haplotype were risk factors for SLE. The gene discussed is HLA-DRB1; the disease is neuromyelitis optica.