In this respect, we acknowledge two limitations of this case study: since we did not perform a targeted sequencing of the FAS gene in sorted DNT cells, we cannot exclude the fact that the immunodysregulatory features shown by the patient were driven by a somatic FAS mutation, a mechanism involved in approximately 20%–30% of ALPS cases with no detectable germline mutation (17); in addition, no functional validation of pathogenicity was available for the two RMRP mutations found in the patient, which are formally considered to be variants of unknown significance. This evidence concerns the gene FAS and autoimmune lymphoproliferative syndrome.