PAX1 and severe combined immunodeficiency: Interestingly, some PAX1 mutations (Cys368*; Asn155del and Val147Leu) (Figure 1) found in OTFCS patients accompanied with severe combined immunodeficiency (SCID), who exhibited not only dysmorphic facial features, malformed vertebral bodies and appendicular structures, but also thymus aplasia, showed reduced transcriptional activity of PAX1 on its target gene (Paganini et al., 2017; Yamazaki et al., 2020).