Newborn screening for severe combined immune deficiency (technical and political aspects)

Severe Combined Immunodeficiency: A Review for Neonatal Clinicians

The proper development and function of T cells is imperative in the creation of adequate cell-mediated and humoral immunity. Healthy term newborns have baseline immune immaturity, increasing their risk of infections, but significant immunologic consequences can occur, because of abnormal T-cell maturation. Combined immunodeficiencies can result, because B cells and natural killer cells rely on successful interactions with T cells to ensure their proper performance and survival. Severe combined immunodeficiency (SCID) is the most noteworthy of these conditions, leading to considerable early morbidity and often death by the age of 1 year if left untreated. Newborn screening for SCID is effective and allows for early implementation of lifesaving supportive measures, including protective isolation, initiation of prophylactic antimicrobials, caution with blood product transfusions, and avoidance of live vaccinations. Once a definitive diagnosis of SCID has been established, treatment frequently involves bone marrow or stem cell transplantation; however, enzyme replacement and gene therapy are also becoming options in those with SCID due to adenosine deaminase deficiency and other forms of SCID. Neonatal clinicians should understand the screening and diagnostic approach to SCID along with the initial management approaches for these extremely high-risk patients.

Societal value of newborn screening for severe combined immune deficiency in Arkansas: An economic analysis

Newborn screening (NBS) is a public health program that detects genetic conditions in neonates enabling treatment before clinical symptoms manifest. Severe combined immune deficiency (SCID) is a primary immune deficiency found in the absence of functioning T and B lymphocytes. Hematopoietic cell transplantation is a potentially curative treatment if received within the first 42 months of life; without treatment, this condition is fatal in the first 2 years of life due to severe opportunistic infections. SCID was added to the recommended uniform panel of conditions for inclusion in state NBS programs in 2010. This manuscript examines the societal costs and benefits of NBS for SCID in Arkansas and implications to health services and social welfare. Total cost per year of all NBS for SCID and resulting early treatment for one patient with SCID in Arkansas is estimated at $1,078,714. Cost of late treatment of one patient with SCID is estimated at $1.43 million. Based on an expected diagnosis of one patient per year in Arkansas, this results in an estimated net cost savings for NBS for SCID in Arkansas of $351,286 per year. Based on cost-effectiveness analysis, NBS for SCID in Arkansas is cost-effective, with higher societal benefit than cost.

The R229Q mutation of Rag2 does not characterize severe immunodeficiency in mice

RAG1 or RAG2 mutations are associated with defects in V(D)J recombination activity, causing severe immunodeficiency with a wide spectrum of clinical phenotypes. A R229Q mutation of RAG2 was identified in patients with severe combined immunodeficiency (SCID) or Omenn syndrome (OS). Although some factors determining the clinical features between SCID and OS were not clear, the molecular mechanism of OS was studied in a mouse model in which an EGFP tag is fused to Rag2 with the R229Q mutation. To design the human disease model mimicking severe immunodeficiency, we generated Rag2-R229Q knock-in mice without an epitope tag. Mutant mice showed impaired T and B cell differentiation with reduced V(D)J recombination activity; however, the extent to which the R229Q mutation affects severe immunodeficiency was not severe. While Rag2-R229Q mutation under some conditions may cause severe immunological and clinical phenotypes similar to human SCID or OS, R229Q mutation per se did not cause severe immunodeficiency in mice, suggesting that additional factors other than R229Q mutation are required to induce severe immunodeficiency. Thus, our report implies that the effects of genetic background and/or a tagged protein sequence may alter the mouse immune system, revealing the mechanism of phenotypic heterogeneity arising from an identical mutation.

A comparison of the incidence of undiagnosed congenital heart disease in hospital born and home born children

OBJECTIVE

To evaluate the incidence of otherwise undiagnosed congenital heart disease (CHD) in a population of children born in a hospital with routine pulse oximetry (RPO) screening compared to children born at home.

METHODS

We reviewed 15 years of births at 2 hospitals for incidence of undiagnosed CHD with RPO. The Health Department reviewed the same data for out of hospital births.

RESULTS

A total of 50,545 hospital births were screened and 1,274 children were born outside the hospital. There were 28 hospital-born babies diagnosed with cyanotic CHD prior to nursery discharge. Only one of these babies would not have been diagnosed without RPO. Three children were missed and there were 3 false positives. Sensitivity and positive predictive value of RPO was 25%, specificity and negative predictive value of RPO exceed 99%. The incidence of CHD requiring RPO diagnosis was roughly one birth per 50,000. Two children born at home with undiagnosed CHD were missed. One of these children presented with neonatal demise.

CONCLUSION

RPO screening is still valuable in diagnosing CHD only diagnosable with RPO. However, the incidence of CHD requiring RPO to diagnose is similar to other congenital diseases which are not mandated national screening tests. In our limited experience a patient is roughly 25 times more likely to have undiagnosed CHD if they are born outside of a hospital.

Stem cell transplantation for the treatment of immunodeficiency in children: current status and hopes for the future

Primary immunodeficiencies (PID) are rare inherited disorders affecting immune function and can be life-threatening if not treated. Haematopoietic stem cell transplantation (HSCT) offers a curative approach for many of these disorders and gene therapy is increasingly used as an alternative therapeutic strategy for patients lacking a suitable donor. Early diagnosis, improved supportive care and advances in gene and cell therapies have resulted in increased survival rates and improved quality of life. This review describes current strategies employed to improve outcomes in PID, focusing on new developments in HSCT, gene and cell therapy. We also address the challenges associated with newborn screening (NBS) programmes and novel mutations identified through improved diagnostic technology.