SFTPA2 and infection: Based on the multiple intragenic and intergenic interactions of SFTPA1 and SFTPA2 observed in the present study, we speculate that innate immunity and host defense play a major role in pediatric ARF and interactions of these two genes with other SP genes play a major role in disease progression, as infection was the most common cause of ARF in our cohort (86% of ARF children had a diagnosis of RSV bronchiolitis, non-RSV bronchiolitis, and pneumonia, see Table 1).