There was a lower incidence of PAX5 and IKZF1 deletions in patients with DS‐associated CRLF2‐r ALL compared to those without DS (18% vs. 35% P < .047 and 23% vs. 53%, P = .003, respectively) (Figure 1C, Supporting Information Table 5). Here, IKZF1 is linked to acute lymphoblastic leukemia.