The case for severe combined immunodeficiency (SCID) and T cell lymphopenia newborn screening: saving lives…one at a time

Current Status of Newborn Bloodspot Screening Worldwide 2024: A Comprehensive Review of Recent Activities (2020-2023)

Newborn bloodspot screening (NBS) began in the early 1960s based on the work of Dr. Robert "Bob" Guthrie in Buffalo, NY, USA. His development of a screening test for phenylketonuria on blood absorbed onto a special filter paper and transported to a remote testing laboratory began it all. Expansion of NBS to large numbers of asymptomatic congenital conditions flourishes in many settings while it has not yet been realized in others. The need for NBS as an efficient and effective public health prevention strategy that contributes to lowered morbidity and mortality wherever it is sustained is well known in the medical field but not necessarily by political policy makers. Acknowledging the value of national NBS reports published in 2007, the authors collaborated to create a worldwide NBS update in 2015. In a continuing attempt to review the progress of NBS globally, and to move towards a more harmonized and equitable screening system, we have updated our 2015 report with information available at the beginning of 2024. Reports on sub-Saharan Africa and the Caribbean, missing in 2015, have been included. Tables popular in the previous report have been updated with an eye towards harmonized comparisons. To emphasize areas needing attention globally, we have used regional tables containing similar listings of conditions screened, numbers of screening laboratories, and time at which specimen collection is recommended. Discussions are limited to bloodspot screening.

Screening Newborns for Low T Cell Receptor Excision Circles (TRECs) Fails to Detect Immunodeficiency, Centromeric Instability, and Facial Anomalies Syndrome

BACKGROUND

Assessment of T-cell receptor excision circles (TRECs) in dried blood spots of newborns allows the detection of severe combined immunodeficiency (SCID) (T cells <300/μL at birth) with a presumed sensitivity of 100%. TREC screening also identifies patients with selected combined immunodeficiency (CID) (T cells >300/μL, yet <1500/μL at birth). Nevertheless, relevant CIDs that would benefit from early recognition and curative treatment pass undetected.

OBJECTIVE

We hypothesized that TREC screening at birth cannot identify CIDs that develop with age.

METHODS

We analyzed the number of TRECs in dried blood spots in archived Guthrie cards of 22 children who had been born in the Berlin-Brandenburg area between January 2006 and November 2018 and who had undergone hematopoietic stem-cell transplantation (HSCT) for inborn errors of immunity.

RESULTS

All patients with SCID would have been identified by TREC screening, but only 4 of 6 with CID. One of these patients had immunodeficiency, centromeric instability, and facial anomalies syndrome type 2 (ICF2). Two of 3 patients with ICF whom we have been following up at our institution had TREC numbers above the cutoff value suggestive of SCID at birth. Yet all patients with ICF had a severe clinical course that would have justified earlier HSCT.

CONCLUSIONS

In ICF, naïve T cells may be present at birth, yet they decline with age. Therefore, TREC screening cannot identify these patients. Early recognition is nevertheless crucial, as patients with ICF benefit from HSCT early in life.

Activated PI3Kδ syndrome - reviewing challenges in diagnosis and treatment

Activated PI3Kδ syndrome (APDS) is a rare inborn error of immunity (IEI) characterized primarily by frequent infections, lymphoproliferation and autoimmunity. Since its initial description in 2013, APDS has become part of the growing group of nearly 500 IEIs affecting various components of the immune system. The two subtypes of APDS - APDS1 and APDS2 - are caused by variants in the PIK3CD and PIK3R1 genes, respectively. Due to the rarity of the disease and the heterogeneous clinical picture, many patients are not diagnosed until years after symptom onset. Another challenge is the large number of PIK3CD and PIK3R1 variants whose functional significance for developing APDS is inconclusive. Treatment of APDS has so far been mostly symptom-oriented with immunoglobulin replacement therapy, immunosuppressive therapies and antibiotic or antiviral prophylaxes. Additionally, allogeneic stem cell transplantation as well as new targeted therapies are options targeting the root cause that may improve patients' quality of life and life expectancy. However, the clinical course of the disease is difficult to predict which complicates the choice of appropriate therapies. This review article discusses diagnostic procedures and current and future treatment options, and highlights the difficulties that physicians, patients and their caretakers face in managing this complex disease. This article is based on cohort studies, the German and US guidelines on the management of primary immunodeficiencies as well as on published experience with diagnosis and compiled treatment experience for APDS.

Immune globulin usage trends in commercially insured and Medicare populations, 2009-2019

BACKGROUND

Longitudinal patterns of immune globulins (IG) use have not been described in large populations. Understanding IG usage is important given potential supply limitations impacting individuals for whom IG is the sole life-saving/health-preserving therapy. The study describes US IG utilization patterns from 2009 to 2019.

STUDY DESIGN AND METHODS

Using IBM MarketScan commercial and Medicare claims data, we examined four metrics overall and by condition-specific categories during 2009-2019: (1) IG administrations per 100,000 person-years, (2) IG recipients per 100,000 enrollees, (3) average annual administrations per recipient, and (4) average annual dose per recipient.

RESULTS

In the commercial and Medicare populations respectively: IG administrations per 100,000 person-years increased by 120% (213-470) and 144% (692-1693); IG recipients per 100,000 enrollees grew by 71% (24-42) and 102% (89-179); average annual administrations per recipient rose by 28% (8-10) and 19% (8-9); and average annual dose (grams) per recipient increased by 29% (384-497) and 34% (317-426). IG administrations associated with immunodeficiency (per 100,000 person-years) increased by 154% (from 127 to 321) and 176% (from 365 to 1007). Autoimmune and neurologic conditions were associated with higher annual average administrations and dose than other conditions.

DISCUSSION

IG use increased, coinciding with a growth in the IG recipient population in the United States. Several conditions contributed to the trend, with the largest increase observed among immunodeficient individuals. Future investigations should assess changes in the demand for IVIG by disease state or indication and consider treatment effectiveness.

Can we identify WHIM in infancy? Opportunities with the public newborn screening process

Newborn screening (NBS) for severe combined immunodeficiency (SCID) utilizing T-cell receptor excision circles (TRECs) has been implemented in all 50 states as of December 2018 and has been transformative for the clinical care of SCID patients. Though having high sensitivity for SCID, NBS-SCID has low specificity, therefore is able to detect other causes of lymphopenia in newborns including many inborn errors of immunity (IEIs). In a recent study, three of six newborns later diagnosed with Warts, Hypogammaglobulinemia, Infections, and Myelokathexis (WHIM) syndrome were found to have a low TRECs and lymphopenia at birth. This presents an opportunity to increase the detection and diagnosis of WHIM syndrome by NBS-SCID with immunological follow-up along with a combination of flow cytometry for immune cell subsets, absolute neutrophil count, and genetic testing, extending beyond the conventional bone marrow studies. Coupled with emerging technologies such as next-generation sequencing, transcriptomics and proteomics, dried blood spots used in NBS-SCID will promote earlier detection, diagnosis, and therefore treatment of IEIs such as WHIM syndrome.

Study Design for an Evaluation of Newborn Screening for SCID in the UK

Severe combined immunodeficiency is a rare inherited disorder, which, if untreated, invariably proves fatal in late infancy or early childhood. With treatment, the prognosis is much improved. Early treatment of the siblings of cases, before they become symptomatic, has shown considerable improvements in outcomes. Based on this and the development of a test that can be used on the whole population of neonates (measurement of T-cell receptor excision circles-TRECs), many countries have added it to their routine newborn bloodspot screening programmes. The UK National Screening Committee (UKNSC) has considered whether SCID should be added to the UK screening programme and concluded that it was likely to be cost effective, but that there were a number of uncertainties that should be resolved before a national roll-out could be recommended. These include some aspects of the test, such as: cost; the use of different assays and cut-off levels to reduce false positive rates, while maintaining sensitivity; the overall benefits of screening for disease outcome in patients with SCID and other identified disorders; the need for a separate pathway for premature babies; the acceptability of the screening programme to parents of babies who have normal and abnormal (both true and false positive) screening results. To achieve this, screening of two thirds of babies born in England over a two-year period has been planned, beginning in September 2021. The outcomes and costs of care of babies identified by the screening will be compared with those of babies identified with SCID in the rest of the UK. The effect of the screening programme on parents will form part of a separate research project.

Awareness of primary immunodeficiency diseases at a national pediatric reference center in Peru

Objective

To investigate the level of awareness of primary immunodeficiency diseases among physicians working at Instituto Nacional de Salud del Niño.

Methods

Cross-sectional study including pediatric residents and pediatricians working at the Instituto Nacional de Salud del Niño during the study period (2017-2019). Physicians working at the immunology unit and surgery departments were excluded. Three aspects of awareness of primary immunodeficiency diseases were investigated: education, general knowledge, and diagnostic suspicion and actions taken in the face of suspicion.

Results

This sample comprised 83 physicians with a median age of 33 years. Most physicians were women (71.1%) and half were pediatric residents. During their undergraduate studies, 43.1% had taken primary immunodeficiency disease courses, and 39.2% had attended conferences on this topic. During their residency training, 25.9% had taken primary immunodeficiency disease courses, and 60.3% had participated in conferences on this topic. Among pediatricians, 50% had taken primary immunodeficiency disease courses, and 53.1% had attended conferences on this topic. Only 39.8% of physicians reported being familiar with the list of 10 warning signs developed by the Jeffrey Modell Foundation. More than half of physicians considered the lack of access to laboratory tests the major challenge in making diagnosis of primary immunodeficiency diseases.

Conclusion

This study revealed limited awareness of primary immunodeficiency diseases among physicians working at Instituto Nacional de Salud del Niño. Although most physicians suspected primary immunodeficiency diseases in patients with a history of recurrent infections and frequent use of antibiotics, not all of them were familiar with the list of 10 warning signs proposed by the Jeffrey Modell Foundation, nor were they able to describe ancillary tests requested in suspected cases.

Multidisciplinary Management of Ataxia Telangiectasia: Current Perspectives

Ataxia telangiectasia (A-T) is a rare autosomal recessive disease caused by mutations in the ataxia telangiectasia mutated (ATM) gene. In the absence of a family history, the diagnosis of A-T is usually not made until the child is older and symptomatic. Classic A-T is characterized by a constellation of clinical symptoms including progressive ataxia, oculocutaneous telangiectasias and sinopulmonary disease and is usually associated with absence of ATM protein. Other laboratory features associated with A-T include elevated serum levels of alpha-fetoprotein (AFP) and increased chromosomal breakage with in vitro exposure to ionizing radiation. Sinopulmonary symptoms can occur to varying degrees across the lifespan. Some children will also have hypogammaglobulinemia and impaired antibody responses requiring supplemental gamma globulin. People with hypomorphic ATM mutations are often considered to have mild A-T with onset of ataxia and neurological progression occurring later in life with less impairment of the immune system. The risk of malignancy, however, is significantly increased in people with either classic or mild A-T. While hematological malignancies are most common in the first two decades of life, solid organ malignancies become increasingly common during young adulthood. Deterioration of neurologic function with age is associated with dysphagia with aspiration, growth faltering, loss of ambulation and decline in pulmonary function, morbidities that contribute to shortened life expectancy and decreased quality of life. Premature death is often due to malignancies or chronic respiratory insufficiency. A-T is currently managed with supportive care and symptomatic treatment. Current clinical trials, however, represent progress and hope towards disease-modifying therapies for A-T.

Newborn screening programs for spinal muscular atrophy worldwide: Where we stand and where to go

Spinal muscular atrophy (SMA) is a rare and devastating disease. New disease-modifying treatments have recently been approved and early treatment has been related to a better outcome. In this context, several newborn screening (NBS) programs have been implemented. The aim of the study was to obtain a global overview on the current situation and perspectives on SMA NBS. We conducted a survey and contacted experts from 152 countries, from which we gathered 87 responses. We identified 9 SMA NBS programs that have so far detected 288 newborns with SMA out of 3,674,277 newborns screened. Funding, screening methods, organisation, and consent process were variable between SMA NBS programs. Many respondents pointed the lack of cost/benefit data as a major obstacle to SMA NBS implementation. In the next four years, our data suggest a 24% coverage of newborns from countries where a disease-modifying drug is available and 8,5% coverage in countries with no diseases-modifying drugs. The annual proportion of newborns to be screened in the coming years is expected to increase steadily. The experts expressed a strong need for the implementation of SMA NBS as means to improve care for patients with SMA.

Pulmonary Manifestations of Immunodeficiency and Immunosuppressive Diseases Other than Human Immunodeficiency Virus

Immune deficiencies may alter normal lung function and protective mechanisms, resulting in a myriad of pulmonary manifestations. Primary immunodeficiencies involve multiple branches of the immune system, and defects may predispose to recurrent upper and lower respiratory infections by common pathogens; opportunistic infections; and autoimmune, inflammatory, and malignant processes that may result in interstitial pneumonias. Secondary immunodeficiencies may result from neoplasms or their treatment, organ transplant and immunosuppression, and from autoimmune diseases and their treatments. Primary and secondary immunodeficiencies and their pulmonary manifestations may be difficult to diagnose and treat. A multidisciplinary approach to evaluation is essential.

Diagnosis of primary immunodeficiencies in Peru

PURPOSE OF REVIEW

Primary immunodeficiencies (PIDs) are human inborn errors of immunity, leading to an increased susceptibility to infections, inflammatory manifestations, and malignancy. We estimate around 16 000 individuals with PIDs living in Peru who are still undiagnosed. The purpose of this review is to make a situational analysis of the diagnosis of PIDs in Peru.

RECENT FINDINGS

There is an evident underdiagnosis of PIDs in Peru. Insufficient awareness and lack of diagnostic tools can be solved partially by expanding the number and expertise of Clinical Immunologists and specialized medical centers. The availability of molecular testing at reasonable costs is mandatory to improve the diagnostic approach to patients with suspected PID. The development of didactic and innovative educational tools has been a critical strategy to improve PID awareness and diagnosis in Peru.

SUMMARY

Developing countries like Peru still have critical limitations to diagnose patients with PIDs such as insufficient awareness in physicians, lack of specialized reference centers, and unavailability of confirmatory genetic testing. Joint work between government, health professionals, patient organizations, and society is essential to overcome these limitations and provide a better future for patients with inborn errors of immunity.

Immune Reconstitution After Gene Therapy Approaches in Patients With X-Linked Severe Combined Immunodeficiency Disease

X-linked severe immunodeficiency disease (SCID-X1) is an inherited, rare, and life-threating disease. The genetic origin is a defect in the interleukin 2 receptor γ chain (IL2RG) gene and patients are classically characterized by absence of T and NK cells, as well as presence of partially-functional B cells. Without any treatment the disease is usually lethal during the first year of life. The treatment of choice for these patients is hematopoietic stem cell transplantation, with an excellent survival rate (>90%) if an HLA-matched sibling donor is available. However, when alternative donors are used, the success and survival rates are often lower. Gene therapy has been developed as an alternative treatment initially using γ-retroviral vectors to correct the defective γ chain in the absence of pre-conditioning treatment. The results were highly promising in SCID-X1 infants, showing long-term T-cell recovery and clinical benefit, although NK and B cell recovery was less robust. However, some infants developed T-cell acute lymphoblastic leukemia after the gene therapy, due to vector-mediated insertional mutagenesis. Consequently, considerable efforts have been made to develop safer vectors. The most recent clinical trials using lentiviral vectors together with a low-dose pre-conditioning regimen have demonstrated excellent sustained T cell recovery, but also B and NK cells, in both children and adults. This review provides an overview about the different gene therapy approaches used over the last 20 years to treat SCID-X1 patients, particularly focusing on lymphoid immune reconstitution, as well as the developments that have improved the process and outcomes.

The challenges presented by haematopoietic stem cell transplantation in children with primary immunodeficiency

INTRODUCTION OR BACKGROUND

For many primary immunodeficiencies (PIDs), haematopoietic stem cell transplantation (HSCT) offers treatment to cure disease. However, patients with PID present a unique set of challenges when considering HSCT.

SOURCES OF DATA

Review of recent literature.

AREAS OF AGREEMENT

The most significant recent impact on successful outcome is introduction of newborn screening programmes for diagnosis of severe combined immunodeficiency-wider adoption of screening in an increasing number of countries will see further improvements. Other PIDs have better outcomes when treated earlier, before development of co-morbidities-early referral for consideration of HSCT is important. Evolution of conditioning regimens is improving short- and long-term toxicities-targeted busulfan and low-toxicity myeloablative treosulfan regimens deliver good survival with reduced short-term toxicities.

AREAS OF CONTROVERSY

The most radical development, still in clinical trials, is the use of mono-antibody-based conditioning, which eliminates the requirement for chemotherapy and is likely to become much more important in HSCT for non-malignant disease in the future.

GROWING POINTS

Multidisciplinary working for optimum care is essential.

AREAS TIMELY FOR DEVELOPING RESEARCH

International collaborations are important to learn about rare presentations and complications, and to formulate the most effective and safe treatment strategies.