ITPR3 and lymphopenia: In contrast to the typically normal T cell counts in CRAC channelopathies (Badran et al., 2016; Byun et al., 2010; Feske et al., 2006, 2010; Fuchs et al., 2012; Lacruz and Feske, 2015; Lian et al., 2018; McCarl et al., 2009; Picard et al., 2009; Schaballie et al., 2015; Yu et al., 2021), ITPR3 patients have peripheral T cell lymphopenia alongside markers of poor thymic output including negligible RTEs and TREC levels (Table 2 and Fig. 5 B).