The values for IgG glycan traits: G0 (higher); G1, G2 and S (lower) for this child (Fig. 3a, marked as a single black cross) were all outside the range of the euploid 4-year-old children (n = 11), and clearly segregating with 1–5 year-old children with DS on derived glycan trait graphs (Fig. 3a), as well as on two different ways of calculating the Principal Component Analysis (PCA) using directly measured IgG glycan peak values (GP1–GP24) (Fig. 3b), or the PCA using derived IgG glycan trait parameters (Fig. 3c). Here, GTPBP1 is linked to Dravet syndrome.