The importance of IgA’s sialylation is further supported by the observation that, although IgA deficiency is largely asymptomatic in humans, children with this defect are more prone to pseudocroup caused by another sialic-acid binding virus, human parainfluenza 1 virus (Fukushima et al., 2014, Tran et al., 2016). This evidence concerns the gene CD79A and selective IgA deficiency disease.