Hasegawa K, et al. - The link between circulating 25-hydroxyvitamin D (25OHD) levels, nasopharyngeal airway metabolome, and bronchiolitis severity, was investigated in this prospective multicenter study of infants (age <1 year) hospitalized with bronchiolitis. Among 254 metabolites identified, researchers defined a set of 20 metabolites that were associated with lower serum 25OHD and higher vitamin D-binding protein levels. Of these, glycerophosphocholines esterified with proinflammatory fatty acids (palmitate, arachidonate, linoleate, and stearate), sphingomyelins, alpha-hydroxyisovalerate, 2-hydroxybutyrate, and 3-(4-hydroxyphenyl)lactate were shown to be associated with a significantly higher risk of positive pressure ventilation use. Overall, a link was obvious between vitamin D-related airway metabolites and risks of bronchiolitis severity.