HELIOS deficiency and AIOLOS deficiency. (A) Structure of the IKZF2/HELIOS and IKZF3/AIOLOS is depicted, highlighting the N-terminal ZFs (ZF1–ZF4) responsible for DNA binding and the C-terminal ZFs (ZF5–ZF6) involved in homo- and heterodimerization, indicated by gray boxes. Exon boundaries within the structure are marked by dotted lines. Above, disease-causing variants associated with HELIOS and AIOLOS deficiencies are mapped, along with the number of individuals and the corresponding disease penetrance. Below, the clinical phenotypes reported by all known individuals with HELIOS and AIOLOS deficiency are shown. (B) Frequencies of symptomatic individuals for each phenotype are summarized for HELIOS and AIOLOS deficiencies. Color codes represent variant types.