Two male siblings with a novel LRBA mutation presenting with different findings of IPEX syndrome

Current genetic defects in common variable immunodeficiency patients on the geography between Europe and Asia: a single-center experience

Identification of the causes of monogenetic common variable immunodeficiency (CVID) patients has rapidly increased in the last years by means of worldwide availability of appropriate genetic diagnostic methods. However, up to date, very limited numbers of reports demonstrating the role of geography, ethnicity, and consanguinity have been published. Here, we reported the first study of Turkish CVID patients and compared them with the results of three countries from America, Europe, and Asia. A total of 100 children diagnosed as CVID according to the criteria of European Society for Immunodeficiencies were enrolled, and they were genetically analyzed by using targeted next-generation sequencing and whole-exome sequencing. The median age of our patients was 5.8 years (range, 3.0-16.0 years) at clinical diagnosis and 9.0 years (range, 4.8-21.0 years) at the time of genetic diagnosis. The consanguinity rate was 24%. Disease-causing pathogenic variants were defined in 40% of patients in a total of 17 different genes. Sixteen of 40 identified pathogenic variants were novel (40%). We determined 18 surface molecular defects, 10 cytosolic defects, 9 nuclear defects, and 3 others. In our cohort, the most common gene was TACI (15/40 in pathogenic variant identified cases and 15/100 in all cases) followed by the others such as PLCү2, LRBA, TCF3, and STAT1. In contrast to our expectations, our results were more similar to American and European population rather than Asians, although we also have high consanguinity rates and live on the geography between Europe and Asia. Genetic investigation is a great challenge, because of the complexity and heterogeneity of the disease, and each country has to know their own current genetic landscape in CVID for a better and successful management of the patients.

Primary Immune Regulatory Disorders With an Autoimmune Lymphoproliferative Syndrome-Like Phenotype: Immunologic Evaluation, Early Diagnosis and Management

Primary immune regulatory disorders (PIRD) are associated with autoimmunity, autoinflammation and/or dysregulation of lymphocyte homeostasis. Autoimmune lymphoproliferative syndrome (ALPS) is a PIRD due to an apoptotic defect in Fas-FasL pathway and characterized by benign and chronic lymphoproliferation, autoimmunity and increased risk of lymphoma. Clinical manifestations and typical laboratory biomarkers of ALPS have also been found in patients with a gene defect out of the Fas-FasL pathway (ALPS-like disorders). Following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA), we identified more than 600 patients suffering from 24 distinct genetic defects described in the literature with an autoimmune lymphoproliferative phenotype (ALPS-like syndromes) corresponding to phenocopies of primary immunodeficiency (PID) (NRAS, KRAS), susceptibility to EBV (MAGT1, PRKCD, XIAP, SH2D1A, RASGRP1, TNFRSF9), antibody deficiency (PIK3CD gain of function (GOF), PIK3R1 loss of function (LOF), CARD11 GOF), regulatory T-cells defects (CTLA4, LRBA, STAT3 GOF, IL2RA, IL2RB, DEF6), combined immunodeficiencies (ITK, STK4), defects in intrinsic and innate immunity and predisposition to infection (STAT1 GOF, IL12RB1) and autoimmunity/autoinflammation (ADA2, TNFAIP3,TPP2, TET2). CTLA4 and LRBA patients correspond around to 50% of total ALPS-like cases. However, only 100% of CTLA4, PRKCD, TET2 and NRAS/KRAS reported patients had an ALPS-like presentation, while the autoimmunity and lymphoproliferation combination resulted rare in other genetic defects. Recurrent infections, skin lesions, enteropathy and malignancy are the most common clinical manifestations. Some approaches available for the immunological study and identification of ALPS-like patients through flow cytometry and ALPS biomarkers are provided in this work. Protein expression assays for NKG2D, XIAP, SAP, CTLA4 and LRBA deficiencies and functional studies of AKT, STAT1 and STAT3 phosphorylation, are showed as useful tests. Patients suspected to suffer from one of these disorders require rapid and correct diagnosis allowing initiation of tailored specific therapeutic strategies and monitoring thereby improving the prognosis and their quality of life.

Potential protein–phenotype correlation in three lipopolysaccharide-responsive beige-like anchor protein-deficient patients

BACKGROUND

Patients with lipopolysaccharide (LPS)-responsive beige-like anchor protein (LRBA) deficiency have a variety of clinical symptoms, but there is no apparent genotype–phenotype correlation, and patients carrying the same mutations may have different phenotypes. Therefore, it is not easy for doctors to make a decision regarding hematopoietic stem cell transplantation (HSCT) for LRBA-deficient patients. We hypothesized that there may be a protein–phenotype correlation to indicate HSCT for LRBA-deficient patients.

AIM

To report on three Chinese LRBA-deficient patients and determine the correlation between residual protein expression and disease phenotypes.

METHODS

Clinical data of three Chinese LRBA-deficient patients were collected, and protein levels were detected by Western blot analysis. In addition, LRBA mutation information of another 83 previously reported patients was summarized.

RESULTS

All the major clinical findings indicated enteropathy, but patients 1 and 3 presented with more severe symptoms than patient 2. Endoscopy and histology indicated nonspecific colitis for patients 1 and 3 but Crohn's disease-like colitis for patient 2. Compound heterozygous mutations in LRBA were found in patient 1, and homozygous mutations in LRBA were found in patient 2 and patient 3. Only patient 2 responded well to traditional immunosuppressive treatment. Residual expression of the LRBA protein in patients 1 and 3 was very low, but in patient 2, a more than 0.5-fold in expression of the LRBA protein was found compared to that in the control. After HSCT, patient 1 had increased LRBA protein expression. We summarized the genetic information of 86 patients, and the mutations in patients 1 and 3 were novel mutations.

CONCLUSION

We described three Chinese LRBA-deficient patients, two of whom carried novel mutations. These patients had no genotype-phenotype correlations, but their residual LRBA protein expression might be associated with disease outcome and could be an indicator for HSCT.

LRBA deficiency: a rare cause of type 1 diabetes, colitis, and severe immunodeficiency

The biological role of the lipopolysaccharide-responsive beige-like anchor (LRBA) protein associated with the immune system is not to date well known. However, it is thought to regulate the CTLA4 protein, an inhibitory immunoreceptor. Chronic diarrhea, autoimmune disorders, organomegaly, frequent recurrent infections, hypogammaglobulinemia, chronic lung manifestations, and growth retardation are some features of LRBA deficiency. This rare disease is observed as a result of homozygous mutations in the LRBA gene. An 11.3-year-old male patient presented because of short stature and high blood glucose level. He had a previous history of lymphoproliferative disease, chronic diarrhea, and recurrent infections. His parents were first-degree consanguineous relatives. A diagnosis of type 1 diabetes mellitus (T1DM) was added to the preexisting diagnoses of immunodeficiency, recurrent infection, enteropathy, chronic diarrhea, lymphadenopathy, hepatomegaly, and short stature. Genetic analysis revealed a homozygous mutation in the LRBA gene, c.5047C>T (p.R1683*) (p.Arg1683*). Abatacept treatment was started: the patient's hospital admission frequency decreased, and glucose regulation improved. At follow-up, growth hormone (GH) deficiency was diagnosed, although it was not treated because the underlying disease was not under control. Nevertheless, the patient's height improved with abatacept treatment. LRBA deficiency should be considered in the presence of consanguineous marriage, diabetes, immunodeficiency, and additional autoimmune symptoms. LRBA phenotypes are variable even when the same variants in the LRBA gene are present. Genetic diagnosis is important to determine optimal treatment options. In addition to chronic malnutrition and immunosuppressive therapy, GH deficiency may be one of the causes of short stature in these patients.

Case Report: Refractory Autoimmune Gastritis Responsive to Abatacept in LRBA Deficiency

Primary immunodeficiency (PID) with immune dysregulation may present with early onset gastrointestinal autoimmune disorders. When gastrointestinal autoimmunity is associated with multiple extraintestinal immune system dysfunction the diagnosis of PID is straightforward. However, with the advent of next generation sequencing technologies, genetic defects in PID genes have been increasingly recognized even when a single or no extraintestinal signs of immune dysregulation are present. A genetic diagnosis is especially important considering the expanding armamentarium of therapies designed to inhibit specific molecular pathways. We describe a boy with early-onset severe, refractory autoimmune gastritis and biallelic mutations in the LRBA gene causing a premature STOP-codon who was successfully treated with CTLA4-Ig, abatacept, with long term clinical and endoscopic remission. The case underscores the importance to consider a monogenetic defect in early onset autoimmune disorders, since the availability of targeted treatments may significantly improve patient prognosis.

A Review of Autoimmune Enteropathy and Its Associated Syndromes

Autoimmune enteropathy is an extremely rare condition characterized by an abnormal intestinal immune response which typically manifests within the first 6 months of life as severe, intractable diarrhea that does not respond to dietary modification. Affected individuals frequently present with other signs of autoimmunity. The diagnosis is made based on a characteristic combination of clinical symptoms, laboratory studies, and histological features on small bowel biopsy. Autoimmune enteropathy is associated with a number of other conditions and syndromes, most notably immunodysregulation polyendocrinopathy enteropathy X-linked (IPEX) syndrome and autoimmune polyglandular syndrome type 1 (APS-1). Diagnosis and treatment is challenging, and further research is needed to better understand the pathogenesis, disease progression, and long-term outcomes of these conditions.

Identifying Novel Mutations in Iranian Patients with LPS-responsive Beige-like Anchor Protein (LRBA) Deficiency

LPS-responsive beige-like anchor protein (LRBA) deficiency is a monogenic primary immunodeficiency characterized by a heterogeneous spectrum of clinical manifestations associated with immune dysregulation. In this study, we reported clinical, immunologic, and genetic evaluation of two Iranian patients from unrelated families, both suffering from recurrent respiratory tract infections, failure to thrive, interstitial lung disease, autoimmune cytopenia, and hypogammaglobulinemia. Pulmonary abscess in one patient and persistent enteropathy in another were also observed. Further investigations revealed causative mutations in the exon (c.2166_2766del) and intron (c.4730-3 T > G) of the LRBA gene. These results may provide further elucidation of the clinical phenotypes and responsible genetic factors of LRBA deficiency.

Clinical, Immunological, and Genetic Features in Patients with Immune Dysregulation, Polyendocrinopathy, Enteropathy, X-linked (IPEX) and IPEX-like Syndrome

BACKGROUND

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a rare inborn error of immunity caused by mutations in the forkhead box P3 (FOXP3) gene.

OBJECTIVE

In this study, we conducted a systematic review of patients with IPEX and IPEX-like syndrome to delineate differences in these 2 major groups.

METHODS

The literature search was performed in PubMed, Web of Science, and Scopus databases, and demographic, clinical, immunologic, and molecular data were compared between the IPEX and IPEX-like groups.

RESULTS

A total of 459 patients were reported in 148 eligible articles. Major clinical differences between patients with IPEX and IPEX-like syndrome were observed in rates of pneumonia (11% vs 31%, P < .001), bronchiectasis (0.3% vs 14%, P < .001), diarrhea (56% vs 42%, P = .020), and organomegaly (10% vs 23%, P = .001), respectively. Eosinophilia (95% vs 100%), low regulatory T-cell count (68% vs 50%), and elevated IgE (87% vs 61%) were the most prominent laboratory findings in patients with IPEX and IPEX-like syndrome, respectively. In the IPEX group, a lower mortality rate was observed among patients receiving hematopoietic stem cell transplantation (HSCT) (24%) compared with other patients (43%), P = .008; however, in the IPEX-like group, it was not significant (P = .189).

CONCLUSIONS

Patients with IPEX syndrome generally suffer from enteropathy, autoimmunity, dermatitis, eosinophilia, and elevated serum IgE. Despite similarities in their clinical presentations, patients with IPEX-like syndrome are more likely to present common variable immunodeficiency-like phenotype such as respiratory tract infections, bronchiectasis, and organomegaly. HSCT is currently the only curative therapy for both IPEX and IPEX-like syndrome and may result in favorable outcome.

Novel compound heterozygous stop-gain mutations of LRBA in a Vietnamese patient with Common Variable Immune Deficiency

Background

Lipopolysaccharide‐responsive and beige‐like anchor (LRBA) deficiency is a rare autosomal recessive common variable immunodeficiency (CVID), affecting 1:25,000–1:50,000 people worldwide. Biallelic mutations in the gene LRBA have been implicated in affected individuals.

Methods

We report a 16‐year‐old Vietnamese, male patient with recurrent CVID symptoms including chronic diarrhea, interstitial pneumonia, cutaneous granulomatous lesions, hepatosplenomegaly, and finger clubbing. Immunological analyses and whole exome sequencing (WES) were performed to investigate phenotypic and genotypic features.

Results

Immunological analyses revealed hypogammaglobulinemia and low ratios of CD4+/CD8+ T cells. Two novel compound heterozygous stop‐gain mutation in LRBA were identified: c.1933C > T (p.R645X) and c.949C > T (p.R317X). Sanger sequencing confirmed the segregation of these variants from the intact parents. The abolished LRBA protein expression was shown by immunoblot analysis. Subsequent treatment potentially saves the child from the same immune thrombocytopenia which led to his brother's untimely death; likely caused by the same LRBA mutations.

Conclusion

This first report of LRBA deficiency in Vietnam expands our knowledge of the diverse phenotypes and genotypes driving CVID. Finally, the utilization of WES shows great promise as an effective diagnostic for CVID in our setting.

Long-term outcome of LRBA deficiency in 76 patients after various treatment modalities as evaluated by the immune deficiency and dysregulation activity (IDDA) score

BACKGROUND

Recent findings strongly support hematopoietic stem cell transplantation (HSCT) in patients with severe presentation of LPS-responsive beige-like anchor protein (LRBA) deficiency, but long-term follow-up and survival data beyond previous patient reports or meta-reviews are scarce for those patients who do not receive a transplant.

OBJECTIVE

This international retrospective study was conducted to elucidate the longitudinal clinical course of patients with LRBA deficiency who do and do not receive a transplant.

METHOD

We assessed disease burden and treatment responses with a specially developed immune deficiency and dysregulation activity score, reflecting the sum and severity of organ involvement and infections, days of hospitalization, supportive care requirements, and performance indices.

RESULTS

Of 76 patients with LRBA deficiency from 29 centers (median follow-up, 10 years; range, 1-52), 24 underwent HSCT from 2005 to 2019. The overall survival rate after HSCT (median follow-up, 20 months) was 70.8% (17 of 24 patients); all deaths were due to nonspecific, early, transplant-related mortality. Currently, 82.7% of patients who did not receive a transplant (43 of 52; age range, 3-69 years) are alive. Of 17 HSCT survivors, 7 are in complete remission and 5 are in good partial remission without treatment (together, 12 of 17 [70.6%]). In contrast, only 5 of 43 patients who did not receive a transplant (11.6%) are without immunosuppression. Immune deficiency and dysregulation activity scores were significantly lower in patients who survived HSCT than in those receiving conventional treatment (P = .005) or in patients who received abatacept or sirolimus as compared with other therapies, and in patients with residual LRBA expression. Higher disease burden, longer duration before HSCT, and lung involvement were associated with poor outcome.

CONCLUSION

The lifelong disease activity, implying a need for immunosuppression and risk of malignancy, must be weighed against the risks of HSCT.

Abatacept as a Long-Term Targeted Therapy for LRBA Deficiency

BACKGROUND

LPS-responsive beige-like anchor (LRBA) deficiency presents with susceptibility to infections, autoimmunity, and lymphoproliferation. The long-term efficacy of cytotoxic T-lymphocyte-associated antigen 4-immunoglobulin (abatacept) as targeted therapy for its immune dysregulatory features remains to be established.

OBJECTIVE

To determine the clinical and immunologic features of LRBA deficiency and long-term efficacy of abatacept treatment in controlling the different disease manifestations.

METHODS

Twenty-two LRBA-deficient patients were recruited from different immunology centers and followed prospectively. Eighteen patients on abatacept were evaluated every 3 months for long-term clinical and immunologic responses. LRBA expression, lymphocyte subpopulations, and circulating T follicular helper cells were determined by flow cytometry.

RESULTS

The mean age of the patients was 13.4 ± 7.9 years, and the follow-up period was 3.4 ± 2.3 years. Recurrent infections (n = 19 [86.4%]), immune dysregulation (n = 18 [81.8%]), and lymphoproliferation (n = 16 [72.7%]) were common clinical features. The long-term benefits of abatacept in 16 patients were demonstrated by complete control of lymphoproliferation and chronic diarrhea followed by immune dysregulation, most notably autoimmune cytopenias. Weekly or every other week administration of abatacept gave better disease control compared with every 4 weeks. There were no serious side effects related to the abatacept therapy. Circulating T follicular helper cell frequencies were found to be a reliable biomarker of disease activity, which decreased on abatacept therapy in most subjects. However, high circulating T follicular helper cell frequencies persisted in 2 patients who had a more severe disease phenotype that was relatively resistant to abatacept therapy.

CONCLUSIONS

Long-term abatacept therapy is effective in most patients with LRBA deficiency.

Clinical, Immunologic, and Molecular Spectrum of Patients with LPS-Responsive Beige-Like Anchor Protein Deficiency: A Systematic Review

BACKGROUND

LPS-responsive beige-like anchor protein (LRBA) deficiency is a primary immunodeficiency and immune dysregulation syndrome caused by biallelic mutations in the LRBA gene. These mutations usually abrogate the protein expression of LRBA, leading to a broad spectrum of clinical phenotypes including autoimmunity, chronic diarrhea, hypogammaglobulinemia, and recurrent infections.

OBJECTIVE

Our aim was to systematically collect all studies reporting on the clinical manifestations, molecular and laboratory findings, and management of patients with LRBA deficiency.

METHODS

We searched in PubMed, Web of Science, and Scopus without any restrictions on study design and publication time. A total of 109 LRBA-deficient cases were identified from 45 eligible articles. For all patients, demographic information, clinical records, and immunologic and molecular data were collected.

RESULTS

Of the patients with LRBA deficiency, 93 had homozygous and 16 had compound heterozygous mutations in LRBA. The most common clinical manifestations were autoimmunity (82%), enteropathy (63%), splenomegaly (57%), and pneumonia (49%). Reduction in numbers of CD4⁺ T cells and regulatory T cells as well as IgG levels was recorded for 21.6%, 65.6%, and 54.2% of evaluated patients, respectively. B-cell subpopulation analysis revealed low numbers of switched-memory and increased numbers of CD21^low B cells in 73.5% and 77.8% of patients, respectively. Eighteen (16%) patients underwent hematopoietic stem cell transplantation due to the severity of complications and the outcomes improved in 13 of them.

CONCLUSIONS

Autoimmune disorders are the main clinical manifestations of LRBA deficiency. Therefore, LRBA deficiency should be included in the list of monogenic autoimmune diseases, and screening for LRBA mutations should be routinely performed for patients with these conditions.