The shared risk factors for a low IgG or IgM level were increasing age [odds ratio (OR) = 1.13; 95% confidence interval (CI) 1.03–1.23 for low IgG level and OR = 1.33; 95% CI 1.15–1.56 for low IgM level] and hypoalbuminemia (OR = 1.83; 95% CI 1.01–3.33 for low IgG level and OR = 3.17; 95% CI 1.23–8.15 for low IgM level). The gene discussed is CD40LG; the disease is Hypoalbuminemia.