This report illustrates a case that would have been missed in the most common screening algorithms used worldwide in newborn screening (NBS) for severe combined immunodeficiency (SCID). Our patient presented with a clinical picture that suggested a severe inborn error of immunity (IEI). The 6-month-old baby had normal T-cell receptor excision circle (TREC) levels but no measurable level of kappa-deleting recombination excision circles (KRECs) in the NBS sample. A de novo IKZF1-mutation (c.476A>G, p.Asn159Ser) was found. The clinical picture, immunologic workup, and genetic result were consistent with IKZF1-related combined immunodeficiency (CID). Our patient had symptomatic treatment and underwent allogeneic hematopoietic cell transplantation (HCT). IKZF1-related CID is a rare, serious, and early-onset disease; this case provides further insights into the phenotype, including KREC status.
Severe Combined Immunodeficiency , Infant, Newborn , Infant , Humans , Severe Combined Immunodeficiency/diagnosis , Severe Combined Immunodeficiency/genetics , Severe Combined Immunodeficiency/therapy , Phenotype , Neonatal Screening , Ikaros Transcription Factor/genetics
