Severe combined immunodeficiency disease (SCID) is the most severe form of primary immunodeficiency disorders (PID). T-cell receptor excision circle (TREC) copy number analysis is an efficient tool for population-based newborn screening (NBS) for SCID and other T cell lymphopenias. We sought to assess the incidence of SCID among Saudi newborn population and examine the feasibility of using targeted next generation sequencing PID gene panel (T-NGS PID) on DNA isolated from dried blood spots (DBSs) in routine NBS programs as a mutation screening tool for samples with low TREC count. Punches from 8,718 DBS collected on Guthrie cards were processed anonymously for the TREC assay. DNA was extracted from samples with confirmed low TREC count, then screened for 22q11.2 deletion syndrome by real-time polymerase chain reaction and for mutations in PID-related genes by T-NGS PID panel. Detected mutations were confirmed by Sanger sequencing. Sixteen out of the 8,718 samples were confirmed to have low TREC copy number. Autosomal recessive mutations in AK2, JAK3, and MTHFD1 were confirmed in three samples. Two additional samples were positive for the 22q11.2 deletion syndrome. In this study, we provide evidence for high incidence of SCID among Saudi population (1/2,906 live births) and demonstrate the feasibility of using T-NGS PID panel on DNA extracted from DBSs as a new reliable, rapid, and cost-effective mutation screening method for newborns with low TREC assay, which can be implemented as part of NBS programs for SCID.

Middle East and North Africa region (MENA) populations are of different ethnic origins. Consanguineous marriages are common practice with an overall incidence ranging between 20 to 50%. Primary immunodeficiency diseases (PIDs) are a group of heterogeneous genetic disorders caused by defects in the immune system that predispose patients to recurrent infections, autoimmune diseases and malignancies. PIDs are more common in areas with high rates of consanguineous marriage since most have an autosomal recessive mode of inheritance. Studies of PIDs in the region had contributed into the discovery and the understanding of several novel immunodeficiency disorders. Few MENA countries have established national registries that helped in estimating the prevalence and defining common PIDs phenotypes. Available reports from those registries suggest a predominance of combined immunodeficiency disorders in comparison to antibody deficiencies seen in other populations. Access to a comprehensive clinical immunology management services is limited in most MENA countries. Few countries had established advanced clinical immunology service, capable to provide extensive genetic testing and stem cell transplantation for various immunodeficiency disorders. Newborn screening for PIDs is an essential need in this population considering the high incidence of illness and can be implemented and incorporated into existing newborn screening programs in some MENA countries. Increased awareness, subspecialty training in clinical immunology and establishing collaborating research centers are necessary to improve patient care. In this review we highlight some of the available epidemiological data, challenges in establishing diagnosis, and available therapy for PID patients in the region.

Combined immunodeficiencies are a heterogeneous collection of primary immune disorders that exhibit defects in T cell development or function, along with impaired B cell activity even in light of normal B cell maturation. CARMIL2 (RLTPR) is a protein involved in cytoskeletal organization and cell migration, which also plays a role in CD28 co-signaling of T cells. Mutations in this protein have recently been reported to cause a novel primary immunodeficiency disorder with variable phenotypic presentations. Here, we describe seven patients from three unrelated, consanguineous multiplex families that presented with dermatitis, esophagitis, and recurrent skin and chest infections with evidence of combined immunodeficiency. Through the use of whole exome sequencing and autozygome-guided analysis, we uncovered two mutations not previously reported (p.R50T and p.L846Sfs) in CARMIL2. Real-time PCR analysis revealed that the biallelic frameshift mutation is under negative selection, likely due to nonsense-mediated RNA decay and leading to loss of detectable protein upon immunoblotting. Protein loss was also observed for the missense mutation, and 3D modeling suggested a disturbance in structural stability due to an increase in the electrostatic energy for the affected amino acid and surrounding residues. Immunophenotyping revealed that patient T_reg counts were significantly depressed, and that CD4⁺ T cells were heavily skewed towards the naïve status. CD3/CD28 signaling impairment was evidenced by reduced proliferative response to stimulation. This work broadens the allelic heterogeneity associated with CARMIL2 and highlights a deleterious missense alteration located outside the leucine-rich repeat of the protein, where all other missense mutations have been reported to date.

Major histocompatibility complex class II (MHC II) deficiency is a rare combined immunodeficiency disease. Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative treatment. Between June 1994 and February 2007, 30 children with MHC II deficiency underwent a total of 33 HSCT procedures. Median age at HSCT was 27 months. The stem cell source was unmanipulated bone marrow from HLA-identical related donors in 26 patients, one HLA antigen-mismatched bone marrow in 3 patients, and unrelated umbilical cord blood in 1 patient. Conditioning was with one of 3 myeloablative regimens--regimen A (18 patients): busulfan (Bu), cyclophosphamide (Cy), and etoposide; regimen B (2 patients): Bu, Cy, and antithymocyte globulin (ATG); or regimen C (1 patient): CY and total body irradiation (TBI)--or with a reduced-intensity regimen (12 patients): fludarabine, melphalan, and ATG. The median CD34 cell dose was 8.3 x 10(6)/kg. Twenty patients experienced immune reconstitution and had sustained engraftment ranging from 9% to 100% for lymphoid lines and from 5% to 100% for myeloid lines that were significant to cure the disease. The overall disease-free survival rate was 66% and 76% after HLA-identical HSCT, with a median follow-up of 6.3 years, which is higher than previously reported. In HLA-identical transplant recipients, reliable donor stem cell engraftment and immune reconstitution were achieved through myeloablative or reduced-intensity conditioning. Further studies and long-term follow-up are needed to determine the appropriate conditioning regimen.