Of the 703 patients with MG and renal damage, 535 had a positive result on serum IFE, among which the most common MIg was IgG λ (n = 140, 26.17%), followed by IgA λ (n = 91, 17.01%) and λ light chain (n = 87, 16.26%). The gene discussed is CD79A; the disease is myasthenia gravis.