Interestingly, polymorphisms in another X-linked gene, namely that encoding the T cell co-stimulatory receptor CD40 ligand (CD40L; CD154), were associated with either an increased (rs3092945: OR (TT vs. CT/CC) = 5.27, 95% CI 1.491–18.621, p = 0.01) or a decreased (rs1126535; OR (TT vs. CT/CC) = 0.331, 95% CI 0.143–0.766, p = 0.006) risk of respiratory distress (supplementary table 3). Here, CD40LG is linked to Respiratory distress.