Although association with various bacterial and viral infections have been reported, such as Cytomegalovirus (Gregory et al., 1988; Waldo et al., 1989), Epstein–Barr virus (Iwama et al., 1998), Haemophilus parainfluenzae (Suzuki et al., 1994), Staphylococcus aureus (Koyama et al., 2004), and streptococcal M protein (Schmitt et al., 2010), it is unclear whether these bacterial and virus form immune complexes with IgA1 and are deposited in glomeruli, whether abnormalities in mucosal immunity result in the production of glomerularly deposited IgA1, or whether the deposition is specific. The gene discussed is IGHA1; the disease is viral infectious disease.