The fifth patient was diagnosed with a novel thymic stromal cell defect due to biallelic pathogenic variants in paired box 1 (PAX1), causing SCID with otofaciocervical syndrome type 2 [23] and was treated at 11 months because of persistent severe T-cell lymphopenia after a period of careful watch and wait. Here, PAX1 is linked to otofaciocervical syndrome 2.