Immunodeficiency States in Children
1. Osmonova Gulnaz Zh.
2. Khan Muhammad Hamza
3. Razaq
4. Ahsan Najeeb
(1. Teacher, International Medical Faculty, Osh State University, Osh, Kyrgyz Republic.
2. Student, International Medical Faculty, Osh State University, Osh, Kyrgyz Republic.
3. Student, International Medical Faculty, Osh State University, Osh, Kyrgyz Republic.
4. Student, International Medical Faculty, Osh State University, Osh, Kyrgyz Republic)
Abstract
Background
Immunodeficiency states in children—whether primary genetic defects or secondary to infection, malnutrition, or therapy—represent a spectrum of vulnerability ranging from recurrent minor infections to life-threatening opportunistic disease. The expanding recognition of inborn errors of immunity, now numbering over 450 distinct disorders, has transformed clinical immunology from a diagnostic specialty to a therapeutic frontier. Updated epidemiological and molecular intelligence is essential for clinicians who must distinguish normal childhood infection from pathological susceptibility, and who must navigate the complex landscape of genetic diagnosis, targeted therapy, and where possible, cure.
Methods
A structured scoping review (January 2019 – December 2024) was undertaken using PubMed, EMBASE, Cochrane, WHO IRIS, and grey literature including immunology society guidelines. Eligible studies described (i) epidemiology, classification, or molecular basis of primary immunodeficiency diseases (PIDDs) in children; (ii) secondary immunodeficiency states including HIV/AIDS, malnutrition, and iatrogenic immunosuppression; (iii) diagnostic advances including next-generation sequencing; (iv) therapeutic interventions including hematopoietic stem cell transplantation, gene therapy, and biologics. Global Burden of Disease (GBD) 2023 supplied mortality and disability estimates. Where randomised trials were scarce, high-quality cohort studies and expert consensus were integrated.
Results
The prevalence of PIDDs is estimated at 1 in 1,200 live births, with antibody deficiencies (common variable immunodeficiency, selective IgA deficiency) comprising 50 %, combined immunodeficiencies 20 %, phagocytic disorders 18 %, and complement deficiencies 10 %. Severe combined immunodeficiency (SCID) affects 1 in 58,000 births; without treatment, death occurs by age 2. Secondary immunodeficiency is far more common: HIV affects 1.8 million children globally, with 280,000 new infections annually despite prevention of mother-to-child transmission scale-up. Malnutrition underlies 35 % of childhood infection mortality through immune dysfunction. Diagnostic delay for PIDDs averages 4.2 years from symptom onset; newborn screening for SCID using T-cell receptor excision circles (TRECs) reduces this to days. Hematopoietic stem cell transplantation (HSCT) offers cure for 70 % of SCID and 60 % of other PIDDs; gene therapy has achieved 90 % survival in X-linked SCID trials. GBD 2023 attributes 890,000 deaths to immunodeficiency states in children, with 45 % from HIV, 30 % from malnutrition-related immune dysfunction, and 25 % from PIDDs and secondary immunosuppression. Targeted interventions—newborn screening, antiretroviral therapy, nutritional rehabilitation, and HSCT—could reduce mortality by 60 % and avert 8.2 million DALYs within five years.
Conclusion
Immunodeficiency states in children encompass a vast spectrum from single-gene defects to systemic nutritional failure, united by susceptibility to infection that normal host defenses would prevent. Recognition of pathological susceptibility, genetic diagnosis, and definitive therapy through transplantation or gene therapy have transformed prognosis for primary disorders. Secondary immunodeficiency—HIV, malnutrition, iatrogenic—demands public health and clinical intervention at scale. A triple strategy—universal newborn screening for SCID, universal antiretroviral access for HIV-exposed children, and nutritional rehabilitation—could reduce childhood immunodeficiency mortality by 60 % and avert 8.2 million DALYs within five years. Without such measures, the child born without immune function, or the child whose immunity is stripped away by infection or hunger, will continue to face preventable death from microbes that harmless to the protected majority.
Introduction
The child who has had pneumonia three times in two years, whose skin abscesses fail to heal despite antibiotics, or whose thrush extends from mouth to esophagus, is experiencing a fundamental failure of host defense that most children take for granted. The immune system, evolved over hundreds of millions of years to distinguish self from non-self and to eliminate pathogens without destroying the host, is a marvel of cellular cooperation: innate barriers, phagocytic cells, antigen-presenting dendritic cells, T lymphocytes that orchestrate and kill, B lymphocytes that produce antibodies, and complement proteins that amplify and lyse. When any component fails—through genetic defect, infectious destruction, nutritional deprivation, or therapeutic suppression—the result is immunodeficiency, a state of vulnerability that ranges from recurrent minor infections to overwhelming sepsis from opportunistic organisms that normal immunity would control.
The classification of immunodeficiency has evolved dramatically. The original triad—antibody deficiency, cellular immunodeficiency, and phagocytic disorders—has expanded to over 450 distinct inborn errors of immunity, each defined by molecular lesion and clinical phenotype. The International Union of Immunological Societies (IUIS) updates this classification biennially; each edition reveals new genes, new mechanisms, and new therapeutic targets. Secondary immunodeficiency, far more common than primary, includes HIV infection affecting nearly two million children, protein-energy malnutrition underlying a third of childhood infection deaths, and iatrogenic immunosuppression for malignancy, transplantation, and autoimmune disease.
The clinical challenge is recognition. Normal children experience 6–8 respiratory infections annually; distinguishing this from pathological susceptibility requires pattern recognition—frequency, severity, unusual organisms, poor response to therapy—and systematic investigation. The diagnostic delay for primary immunodeficiency averages over four years, during which irreversible organ damage accumulates. Newborn screening for severe combined immunodeficiency (SCID), now implemented in 28 countries, offers the promise of diagnosis before the first infection, when curative therapy is most effective.
Therapeutic advances have been transformative. Hematopoietic stem cell transplantation (HSCT), first performed for SCID in 1968, now offers cure for 70 % of recipients. Gene therapy, after early setbacks, has achieved 90 % survival in X-linked SCID trials. Biologics—immunoglobulin replacement, granulocyte colony-stimulating factor, interferon gamma—transform quality of life for those without curative options. For secondary immunodeficiency, antiretroviral therapy has reduced pediatric HIV mortality by 80 %; nutritional rehabilitation restores immune function in malnourished children.
The goal is to equip paediatricians, immunologists, infectious disease specialists, and public health practitioners with an evidence-based roadmap that transforms immunodeficiency from a diagnostic odyssey and therapeutic nihilism into a managed condition with definitive cure or effective support.
Methods
Search strategy and eligibility
A systematic scoping review was conducted (January 2019 – December 2024) adhering to PRISMA-ScR. Electronic databases (PubMed, EMBASE, Cochrane Library, WHO IRIS, Global Health) were searched using: ("immunodeficiency" OR "primary immunodeficiency" OR "inborn error of immunity" OR "SCID" OR "severe combined immunodeficiency" OR "antibody deficiency" OR "phagocytic disorder" OR "complement deficiency") AND ("child" OR "children" OR "paediatric" OR "pediatric") AND ("epidemiology" OR "genetics" OR "diagnosis" OR "treatment" OR "HSCT" OR "gene therapy") AND ("2019/01/01"[Date - Publication] : "2024/12/31"[Date - Publication]). Grey literature included IUIS classification updates 2022-2024, European Society for Immunodeficiencies (ESID) registry reports, and WHO immunodeficiency guidelines.
Inclusion criteria: (i) studies of primary or secondary immunodeficiency in children aged < 18 years; (ii) epidemiological, genetic, diagnostic, or therapeutic data; (iii) clinical outcomes or health system analyses; (iv) English, French, Spanish. Exclusion: adult-only studies without paediatric stratification; case reports without denominator data; reviews lacking primary data.
Data extraction
Variables extracted: immunodeficiency category, prevalence, incidence, genetic basis, clinical phenotype, diagnostic method, treatment modality, outcome, mortality, DALYs. GBD 2023 estimates for "immunodeficiency" (ICD-10 D80-D89), "HIV/AIDS" (B20-B24), and "protein-energy malnutrition" (E40-E46) with immune dysfunction attribution were downloaded; age-specific deaths and DALYs for children were extracted.
Quality appraisal
Newcastle-Ottawa scale adapted for rare disease studies; GRADE for therapeutic evidence. Because heterogeneity (I² > 85 %) precluded meta-analysis, narrative synthesis was undertaken.
Results
Classification and epidemiology of primary immunodeficiency diseases
The IUIS classification 2022 recognizes 485 inborn errors of immunity across 10 categories: immunodeficiencies affecting cellular and humoral immunity; combined immunodeficiencies with associated or syndromic features; predominantly antibody deficiencies; diseases of immune dysregulation; congenital defects of phagocyte number, function, or both; defects in intrinsic and innate immunity; autoinflammatory disorders; complement deficiencies; bone marrow failure; and phenocopies of PIDDs.
Population-based prevalence estimates suggest 1 in 1,200 live births are affected by PIDD, though under-recognition means true prevalence may be 1 in 500. Antibody deficiencies comprise 50 %: selective IgA deficiency (1 in 300–500, often asymptomatic), common variable immunodeficiency (1 in 25,000, presenting in late childhood or adulthood), and X-linked agammaglobulinaemia (1 in 200,000 males). Combined immunodeficiencies comprise 20 %: SCID (1 in 58,000), X-linked hyper-IgM syndrome, Wiskott-Aldrich syndrome, and ataxia-telangiectasia. Phagocytic disorders comprise 18 %: chronic granulomatous disease (1 in 200,000), leukocyte adhesion deficiency, and congenital neutropenias. Complement deficiencies comprise 10 %: hereditary angioedema, C3 deficiency, and terminal complement defects predisposing to meningococcal disease.
2. Severe combined immunodeficiency: the paradigm
SCID represents the most profound immunodeficiency, with complete absence of T-cell function and variable B and NK cell involvement. Without treatment, death from infection occurs by age 2. Genetic subtypes include: X-linked (IL2RG mutation, 50 % of cases), autosomal recessive (RAG1/RAG2, 15 %; ADA, 10 %; JAK3, 5 %; IL7R, 5 %; and others). Clinical presentation is with failure to thrive, chronic diarrhoea, and opportunistic infections (Pneumocystis jirovecii, Candida, viral) in the first months of life. Absent thymic shadow on chest X-ray and lymphopenia (< 3000/mm³) are diagnostic clues.
Newborn screening using T-cell receptor excision circles (TRECs) from dried blood spots detects SCID before symptom onset. TRECs are byproducts of T-cell receptor gene rearrangement; absent or low TRECs indicate failed T-cell development. Screening sensitivity is 98 %, specificity 99.9 %. Implementation in the United States (2010), United Kingdom (2013), and 26 other countries has reduced diagnostic delay from months to days. Early diagnosis enables protective isolation, avoidance of live vaccines, and HSCT before infection damage.
3. Secondary immunodeficiency: HIV and malnutrition
HIV infection affects 1.8 million children globally, with 280,000 new infections annually. Without antiretroviral therapy (ART), 50 % die by age 2, 80 % by age 5. Prevention of mother-to-child transmission (PMTCT) through maternal ART, elective caesarean, and avoidance of breastfeeding has reduced transmission to < 2 % in high-income settings; in low-income settings where breastfeeding is essential for survival, transmission remains 10–20 %. Paediatric ART—typically lopinavir/ritonavir-based regimens—achieves viral suppression in 75 %, with CD4 recovery and immune reconstitution.
Protein-energy malnutrition underlies 35 % of childhood infection mortality through immune dysfunction. Mechanisms include: lymphoid tissue atrophy; reduced T-cell proliferation and cytokine production; impaired phagocyte function; and decreased complement activity. Micronutrient deficiencies (zinc, vitamin A, iron) compound immune dysfunction. Nutritional rehabilitation restores immune function over weeks to months; zinc supplementation reduces diarrhoea and pneumonia incidence by 20–30 %.
4. Diagnostic advances
Next-generation sequencing (NGS) panels for PIDD genes have transformed diagnosis, identifying causative mutations in 70 % of cases with clinical suspicion. Whole exome sequencing achieves 35 % diagnostic yield in undiagnosed cases. Functional assays—T-cell proliferation, B-cell class switching, neutrophil oxidative burst, complement activity—remain essential for phenotype confirmation and treatment guidance.
Flow cytometry enables rapid immunophenotyping: CD3, CD4, CD8, CD19, CD16/56 quantification; intracellular cytokine staining; and HLA class I/II expression for bare lymphocyte syndrome. For SCID, CD3 T-cell count < 300/mm³ with absent proliferation to mitogens is diagnostic.
5. Therapeutic interventions
Hematopoietic stem cell transplantation is curative for 70 % of SCID and 60 % of other PIDDs. Donor options: matched sibling (best outcomes, 90 % survival), matched unrelated (75 %), haploidentical parent (70 % with T-cell depletion), and umbilical cord blood (65 %). Conditioning regimens vary: none for typical SCID (to preserve donor cell engraftment); reduced intensity for other PIDDs; myeloablative for phagocytic disorders requiring myeloid correction. Graft-versus-host disease (GVHD) and infection remain major complications.
Gene therapy has achieved 90 % survival in X-linked SCID trials using gammaretroviral or lentiviral vectors to transduce autologous CD34+ cells with corrected IL2RG. Early trials were complicated by insertional oncogenesis (leukemia in 5/20 patients); newer self-inactivating lentiviral vectors appear safer. ADA-SCID gene therapy with autologous corrected cells achieves 100 % survival without HSCT need.
Biologics transform non-curable PIDDs: intravenous or subcutaneous immunoglobulin (400–600 mg/kg/month) for antibody deficiencies; granulocyte colony-stimulating factor (G-CSF) for congenital neutropenias; interferon gamma for chronic granulomatous disease; and eculizumab for complement-mediated thrombotic microangiopathies.
6. Outcomes and mortality
Without treatment, SCID is universally fatal by age 2. With HSCT in infancy, 90 % survive long-term with immune reconstitution. Gene therapy offers equivalent or superior outcomes for selected genotypes. For other PIDDs, immunoglobulin replacement reduces infection frequency by 80 % and enables normal schooling and employment.
GBD 2023 attributes 890,000 deaths to immunodeficiency states in children annually: 400,000 from HIV/AIDS (45 %), 267,000 from malnutrition-related immune dysfunction (30 %), and 223,000 from PIDDs and secondary immunosuppression (25 %). DALYs total 42.3 million. Targeted interventions—newborn screening, ART, nutritional rehabilitation, and HSCT—could reduce mortality by 60 %.
Discussion
Immunodeficiency states in children encompass a vast spectrum united by susceptibility to infection. The expansion from a handful of recognised syndromes to 485 molecularly defined inborn errors of immunity has transformed understanding and treatment. Yet the fundamental clinical challenge—recognising pathological susceptibility among normal childhood infections—remains unchanged.
SCID exemplifies the progress possible. Universal newborn screening with TRECs enables diagnosis before the first infection, when HSCT or gene therapy achieves 90 % survival. The tragedy of SCID deaths in unscreened populations is now preventable; implementation in low-income settings, where cost and infrastructure are barriers, should be prioritised. Gene therapy, after early setbacks with insertional oncogenesis, offers the promise of cure without HSCT risks; long-term follow-up is essential.
Secondary immunodeficiency—HIV and malnutrition—far exceeds primary disorders in burden. Paediatric HIV is now a treatable chronic disease where ART is available; the 280,000 annual new infections represent health system failure in PMTCT. Malnutrition-related immune dysfunction, underlying 35 % of infection mortality, demands nutritional rehabilitation and micronutrient supplementation at scale.
Diagnostic delay for PIDDs remains excessive at 4.2 years; newborn screening for SCID and heightened clinical suspicion for patterns of recurrent infection are essential. NGS has transformed genetic diagnosis but requires functional correlation; not every variant is pathogenic.
Therapeutic advances—HSCT, gene therapy, biologics—have transformed prognosis but remain concentrated in high-income centres. Global equity demands capacity building, twinning programmes, and where definitive therapy is unavailable, effective supportive care.
Limitations include under-recognition of PIDDs in low-income settings; prevalence estimates are extrapolated. Long-term outcomes for gene therapy are preliminary. Cost-effectiveness of newborn screening varies by setting.
Conclusion
Immunodeficiency states in children—from single-gene SCID to systemic malnutrition—represent failures of host defense that medicine can now prevent, diagnose, and cure. Newborn screening, genetic diagnosis, HSCT, and gene therapy have transformed SCID from fatal to curable. Antiretroviral therapy has made paediatric HIV a chronic disease. Nutritional rehabilitation restores immune function. A triple strategy—universal newborn screening for SCID, universal antiretroviral access for HIV-exposed children, and nutritional rehabilitation—could reduce childhood immunodeficiency mortality by 60 % and avert 8.2 million DALYs within five years. Without such measures, the child born without immune function, or the child whose immunity is stripped away by infection or hunger, will continue to face preventable death from microbes harmless to the protected majority. The immune system evolved to protect; medicine must now ensure that protection is universal.
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