A novel splice site variant in FOXN1 in a patient with abnormal newborn screening for severe combined immunodeficiency and congenital lymphopenia

Background: The Forkhead box protein N1 (FOXN1) is a key regulator of thymic epithelial development, and its complete deficiency leads to nude-severe combined immunodeficiency (SCID) phenotype. More recently, heterozygous mutations in FOXN1 have been linked with syndrome congenital lymphopenia wide clinical spectrum, most cases being caused by missense mutations. Aim: To broaden the genotypic phenotypic spectrum deficiency. Methods: Case report patient haploinsufficiency due novel splice-site mutation. Results: Our was identified at 3 weeks life given an abnormal newborn screen (NBS) for SCID, found preferentially affecting CD8 + T-cells. Her cellular humoral function were both excellent, she has remained entirely asymptomatic thriving first years her life. on whole exome sequencing carry mutation gene, domain. also mother. Conclusion: Heterozygous are increasingly-recognized cause lymphopenia. experience suggests patients remain clinically well, main manifestation including T-lymphopenia, mostly cells. Identification same variant parent age-dependent improvement T-cell counts overall benign course, while provides impetus diligent conservative management regular follow-up. Statement novelty: relatively new entity, attributed FOXN1. further expand knowledge basis regarding this emerging disorder, as well repertoire, we herein case splice site