Results
In total, 82 individuals participated in screening for IGHG4 gene deletion. The mean ratio of IGHG4 in 23 DS patients with a low IgG4 level was 0.70 (±0.31), which is significantly lower than the mean ratio of IGHG4 in the 21 DS patients with normal IgG4 level at 0.97 (±0.16, P = 0.008 ). The low serum IgG4 patients also differed from the control group (healthy subjects without DS) who had a mean ratio of 0.99 (±0.16), P < 0.001.
In the 23 (52.3%) of DS patients with low serum IgG4, 16 (69.57%) had heterozygous gene deletion, while 7 (30.43%) did not. The lowest value was 0.20 and the highest value was 1.23. For those 21 (47.7%) DS patients with normal IgG4 levels, 19 (90.48%) of the patients had no deletion, while only two patients had the deletion (9.52%; P< 0.001 ). The minimum ratio for patients with normal IgG4 was 0.52 and the maximum ratio was 1.16. In the control group of 38 healthy donors, it was found that only two (5.26 %) had the deletion, whereas 36 (94.74%, P <0.001 ) had no detectable IGHG4 deletion (see Figure 1). In examiningIGHG2 and IGHE among patients with IGHG4 deletion, only one patient (9.09%) presented with both an IGHG2 andIGHE deletion (see Table 1).