SMARCAL1 and Schimke immuno-osseous dysplasia: As SMARCAL1 is expressed in the thymus [7] and works to limit DNA replication damage [10], we hypothesize that that VDJ recombination-induced DNA stress leads to thymic cell death in SIOD patients, resulting in low production of naïve T cells and their accelerated maturation, similarly to other DNA repair defect diseases such as Nijmegen breakage syndrome [11].