The sample sizes of patients with SIgAD, PIgAD, and IgAD patients with IgG subclass deficiency in included articles varied from 4 patients with IgA deficient patients with IgG subclass deficiency of the Affiliated University Children’s Hospital in Berne up to 2100 SIgAD patients in a study through six university hospitals in Sweden. The gene discussed is CD79A; the disease is selective IgA deficiency disease.