Israel Medical Association Journal

Inborn errors of immunity (IEI) result from pathogenic germline variants. These disorders are clinically characterized by increased susceptibility to infections and immune dysregulation, often leading to reduced survival [1]. By linking specific monogenic defects to immune phenotypes, IEI serve as experiments of nature that provide powerful models for dissecting human immunology [2]. The International Union of Immunological Societies (IUIS) currently classifies IEI into 10 major categories with overlapping phenotypes [3]: combined T- and B-cell immunodeficiencies, combined immunodeficiencies with syndromic features, predominantly antibody deficiencies, diseases of immune dysregulation, congenital defects of phagocytes, defects in intrinsic and innate immunity, autoinflammatory diseases, complement deficiencies, bone marrow failure, and phenocopies of IEIs. The recent 2024 IUIS update was designed to serve clinicians and researchers and to inform the design of targeted sequencing panels that facilitate the genetic diagnosis of IEI. It lists 508 genes underlying 559 conditions [3]. Of note, molecular, cellular, and clinical investigations of IEI have transformed our understanding of disease pathogenesis and enabled effective targeted therapies.

The field of inborn errors of immunity (IEI), previously known as primary immune deficiencies, includes susceptibility to infections, autoimmunity, uncontrolled inflammation and malignancy is rapidly expanding. Novel scientific discoveries together with artificial intelligence and machine learning are transformed into advances in the diagnosis and treatment of affected patients. These changes require adjustments in the knowledge, skills and attitudes of health care providers, and particularly expert clinicians managing patients with IEI. In this perspective, we highlighted some of the educational needs that should be adapted to ensure that the next generation of physicians provide best care for those affected by IEI.

Inborn errors of immunity represent a heterogeneous group of disorders with variable clinical manifestations. Within this group of disorders, severe combined immunodeficiency (SCID) is the most profound disorder, where affected infants present clinically early in life, and have almost uniformly fatal outcome unless hematopoietic stem cell transplantation (HSCT) is performed. Gene therapy or enzyme replacement therapy are options in some specific SCID forms [1]. The estimated incidence of SCID in the United States is 1 in 58,000 live births, while in Israel the incidence is as high as 1 in 29,000 live births. This higher rate is due to a high rate of consanguineous marriages in certain communities [2].

Neutrophils serve as a cornerstone of innate immunity. Beyond their classical antimicrobial repertoire, these cells are versatile and capable of shaping the adaptive immune response through direct interactions with dendritic cells and lymphocytes in addition to cytokine-mediated effects. Additional functional phenotypes have also been described with regard to cancer and chronic inflammation. The clinical importance of neutrophils in host defense is perhaps best illustrated by the spectrum of inborn neutrophil disorders, ranging from congenital neutropenia to defects of adhesion and phagocytosis. We present a patient with clinical and laboratory features of hemophagocytic lymphohistiocytosis with a bacterial infection. The patient was subsequently found to carry a homozygous variant in the NCF2 gene, establishing a diagnosis of autosomal recessive chronic granulomatous disease (CGD). This presentation, combining cytokine storm with ongoing infection-driven inflammation, exemplifies the multifaceted role of neutrophils in health and disease. In this review, we provide clinical and immunological insights into neutrophil disorders, illustrated through a case of CGD as a paradigm of primary neutrophil dysfunction.

Background: Syndromic inborn errors of immunity (IEIs) are a heterogeneous group of disorders characterized by immune dysfunction associated with congenital anomalies and multisystem involvement. Tricho-hepato-enteric syndrome (THES) is an ultra-rare autosomal recessive syndromic IEI caused by biallelic pathogenic variants in TTC37 or SKIV2L. Delayed recognition is common because of its broad clinical spectrum.

Objectives: To describe the clinical, immunologic, genetic, and histopathologic characteristics of two children with THES and to highlight a structured diagnostic approach for syndromic immunodeficiencies.

Methods: We retrospectively reviewed the clinical presentation, laboratory investigations, immune phenotyping, endoscopic and histopathologic findings, and molecular analyses of two unrelated children diagnosed with THES at a tertiary pediatric immunology center. Molecular confirmation was obtained by whole-exome sequencing.

Results: Both patients presented during early infancy with intractable diarrhea, severe failure to thrive, characteristic dysmorphic features, brittle woolly hair, and inflammatory enteropathy requiring prolonged nutritional support. Immunologic evaluation demonstrated immune dysregulation, including inverted CD4/CD8 ratios, abnormalities of humoral immunity, and impaired vaccine-specific antibody responses. Histopathology revealed chronic active colitis with crypt distortion, inflammatory infiltrates, and crypt abscesses, consistent with very-early-onset inflammatory bowel disease-like enteropathy. Whole-exome sequencing identified homozygous pathogenic variants in SKIV2L in one patient and TTC37 in the other, establishing the diagnosis. Management included nutritional support, immunoglobulin replacement, antimicrobial prophylaxis, and immunomodulatory therapy.

Conclusions: Recognition of syndromic phenotype combined with comprehensive immune evaluation and early genomic testing facilitates prompt diagnosis, multidisciplinary management, genetic counseling, and consideration of emerging targeted therapies.

Background: Bone marrow failure syndromes (BMFs) comprise a heterogeneous group of genetic disorders characterized by impaired hematopoiesis and multisystem involvement. Dyskeratosis congenita (DC) is a telomere biology disorder caused by defects in telomerase or telomere maintenance, leading to progressive BMF and variable extra-hematopoietic manifestations.

Objectives: To describe the clinical, immunologic, genetic, and telomere biology findings in a patient with DC caused by a novel biallelic telomerase reverse transcriptase (TERT) mutation, and to highlight diagnostic and therapeutic considerations in telomere-associated BMFs.

Methods: We assessed cellular and humoral immune functions. Genetic analysis was conducted using whole-exome sequencing (WES) with segregation analysis. Telomere length was assessed by flow-FISH. Functional and radiologic evaluations were performed to define disease extent.

Results: A 2-year old male born to consanguineous parents presented with multisystemic clinical features, and hypocellular bone marrow. WES identified a novel homozygous TERT missense variant (c.3052G>A; p.Ala109Thr) supported by markedly shortened telomeres. Neuroimaging revealed cerebellar hypoplasia consistent with Hoyeraal-Hreidarsson syndrome. Immunologic evaluation demonstrated skewed CD4:CD8 ratios. An incidental heterozygous MEN1 variant was also detected.

Conclusions: We expand the clinical and genetic spectrum of TERT-associated DC and illustrate the critical role of genomic diagnostics and telomere assessment in BMFs. Early molecular diagnosis enables targeted evaluation, informs prognosis, and guides personalized management in telomere biology disorders. In addition, the identification of actionable secondary variants further highlights both the power and complexity of comprehensive genomic testing.

Inborn errors of immunity (IEI), formerly known as primary immunodeficiencies (PID), comprise a diverse group of genetic disorders characterized by increased susceptibility to infections, autoimmunity, autoinflammatory conditions, allergies, and malignancies. These disorders exhibit a broad spectrum of clinical manifestations, including extra-hematopoietic manifestations, which may also present later in life. IEI diagnosis has significantly advanced, in line with the common use of next-generation sequencing-based genetic platforms, such as whole-exome and whole-genome sequencing. Treatment approaches have evolved beyond infection management to include curative therapies such as hematopoietic stem cell transplantation, gene therapy, and targeted pharmacologic treatments. In this review, we explore recent advancements in the understanding, diagnosis, and treatment of IEI, emphasizing the rapid progress in this expanding field.

Background: Several studies have identified associations between low vitamin D concentrations and risk of upper respiratory infections (URI). T lymphocytes have a major anti-viral role, are affected by vitamin D metabolism, and may mediate the link between vitamin D and URIs. Competitive swimmers have a relatively high rate of URIs, alongside a high prevalence of low vitamin D concentration. 

Objectives: To examine the associations linking T cell receptor excision circles (TREC, markers of thymus activity), circulating 25(OH)D concentrations and the effect of vitamin D supplementation, and URI symptoms in young competitive swimmers.

Methods: We tested 82 adolescent swimmers for serum 25(OH)D and TREC concentrations and found that 55 had vitamin D insufficiency. Randomized supplementation of either vitamin D3 or placebo was given for 12 winter weeks. URI symptoms were recorded weekly. The associations between TREC copy numbers, vitamin D and URI burden were examined.

Results: TREC concentrations decreased with the participants’ age (r = -0.346, P = 0.003), with no significant between-gender difference. TREC concentrations did not materially differ among subjects with normal, insufficient or deficient vitamin D status, and were not affected by vitamin D supplementation. No significant correlations were found between TREC levels or their changes during the study period, and mean URI severity or duration. 

Conclusions: Thymus activity, represented by higher TREC levels, was not related to vitamin D concentrations or status, and was not affected by vitamin D supplementation in adolescent swimmers. TREC concentrations were not associated with URI severity or duration in this population.

 

Objective: To assess the ability of TREC and KREC counts to identify patients with combined T and B cell immunodeficiency in a pilot study in Israel.

Methods: We studied seven children born in Israel during the years 2010–2011 and later diagnosed with SCID, and an additional patient with pure B cell immunodeficiency. TREC and KREC in peripheral blood upon diagnosis and in their neonatal Guthrie cards were analyzed using real-time quantitative polymerase chain reaction, as were Guthrie cards with dried blood spots from healthy newborns and from normal and SCID-like controls.

Results: The first features suggestive of SCID presented at age 3.1 ± 2.4 months in all patients. Yet, the diagnosis was made 4.1 ± 2.9 months later. Their TREC were undetectable or significantly low at their clinical diagnosis and in their originally stored Guthrie cards, irrespective of the amount of their circulating T cells. KREC were undetectable in six SCID patients who displayed B cell lymphopenia in addition to T cell lymphopenia. KREC were also undetectable in one patient with pure B cell immunodeficiency.

Conclusions: TREC and KREC quantification are useful screening tests for severe T and B cell immunodeficiency. Implementation of these tests is highly important especially in countries such as Israel where a high frequency of consanguinity is known to exist. 

Background: Leptin, a pleiotropic hormone, has been suggested to be part of an acute phase response during an inflammatory stimulus. Its correlation with other acute phase reactants during minor infection in children has not been investigated.

Objectives: To study the correlation between serum leptin levels to those of C-reactive protein, a well-documented acute-phase reactant, in a series of pediatric patients with acute minor infections.

Methods: Leptin and CRP[1] levels were measured in 62 blood samples of pediatric patients presenting with mild febrile illness who were admitted to Dana Children’s Hospital in Israel. All children were finally diagnosed as having minor infection based on the negative blood/urine cultures and favorable outcome.

Results: Serum leptin level was positively correlated with CRP (r² = 0.5), total white blood cells (r² = 0.33) and absolute neutrophil count (r² = 0.31). The regression coefficient was the highest between leptin and CRP.

Conclusions: Circulating leptin concentrations are positively correlated with CRP levels during acute minor infection in children visiting the emergency room for febrile illnesses. Our observation suggests that leptin is indeed a part of acute-phase proteins. The wide scattering showed that it is not a better marker in minor infections than CRP, but it may contribute to weight loss and anorexia seen in the minority of patients during mild infections.

Background: The modest clothing that Orthodox Jewish women wear exposes very little of their skin to sunlight. Under these conditions they may develop vitamin D deficiency, even in sunny Israel.

Objectives: To determine and compare the vitamin D nutritional status in Jewish orthodox mothers to that of non-orthodox mothers who live in the same metropolitan area in Israel.

Methods: 25-Hydroxyvitamin D was measured by compe­titive protein-binding radioassay in the sera of 341 Jewish Israeli mothers (156 orthodox and 185 non-orthodox). The sera were obtained 48-72 hours after childbirth during the late summer of 1998 and the spring of 1999.

Results: The mean (SD) serum concentration of 25-OHD was significantly (P<0.002) lower (13.5 ± 7.5 ng/ml) in the orthodox than in the non-orthodox mothers (18.6 + 9.6 ng/ml). Vitamin D deficiency (<5 ng/ml) and insufficiency (<10 ng/ml) were more common in the orthodox mothers (5.1% and 32.7% respectively) than in the non-orthodox mothers (2.7% and 13%, respectively). In subgroups of mothers supplemented with 400 units of vitamin D daily during pregnancy, vitamin D deficiency and insufficiency were less common (2.2% and 13%, respectively) in orthodox and non-orthodox mothers (0% and 8.1%, respectively). Vitamin D insufficiency was more common in the winter than in the summer only among non­orthodox mothers.

Conclusions: The high prevalence of vitamin D deficiency and insufficiency in Israeli mothers raises the question whether vitamin D supplements should be given to pregnant women in Israel, at least to orthodox mothers.
 

Background: Previous reports on the behavior of procalcitonin blood levels in diverse clinical conditions suggest that it is part of the activation of cellular immunity and is another acute-phase reactant.

Objective: To compare procalcitonin with C-reactive protein, a well-known acute-phase reactant, in a series of acutely febrile pediatric patients and to review recent literature on procalcitonin.

Methods: Procalcitonin and CRP levels were evaluated in 38 blood samples of pediatric patients who were admitted to the Dana Children’s Hospital for evaluation of unexplained fever or for sepsis work-up.

Results: The parallelism between procalcitonin and CRP was found to be highly significant (P<0.01).

Conclusion: The rise of procalcitonin blood levels in febrile pediatric patients suggests that it is part of the acute-phase reaction, parallel with the CRP reaction.