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- FREE ACCESSBackground: Lipopolysaccharide-responsive beige-like anchor (LRBA) is an intracellular protein that regulates the recycling of cytotoxic T lymphocyte-associated protein 4 (CTLA4), an immune checkpoint molecule which prevents ongoing activation of T cells. Deficiency of LRBA results in increased trafficking and degradation of CTLA4, and consequently, uncontrolled T cell responses. The phenotypic spectrum of LRBA deficiency arising from biallelic loss-of-function typically includes recurrent infections, autoimmunity, lymphoproliferation, chronic diarrhea, hypogammaglobulinemia, and cytopenia.Aim: To report an atypical presentation of LRBA deficiency arising from a set of compound heterozygous LRBA variants, encompassing recurrent hemophagocytic lymphocytosis (HLH) and neurological manifestations.Methods: Clinical data was gathered through retrospective chart review. Expanded genetic analysis including whole exome sequencing was performed.Results: Our patient initially presented at age 15 months with fever, seizures, and encephalopathy. HLH-work-up showed bicytopenia, elevated ferritin and triglyceride, and low fibrinogen, however, he did not yet meet the diagnostic criteria for HLH. MRI brain and EEG at diagnosis was suggestive of acute necrotizing encephalopathy of childhood. He responded to pulsed IV methylprednisolone treatment with minimal residual neurological deficit on follow-up. At 36 months of age, he had a repeat presentation and rapidly deteriorated. He developed severe encephalopathy with fixed dilated pupils. Whole exome sequencing revealed a set of compound heterozygous missense variants in the LRBA gene, a novel c.2206A>T (p.R736W) and c.5989C>T (p.R1997C) variant.Conclusion: Compound heterozygous mutations in the LRBA gene caused an atypical presentation of recurrent HLH with central nervous system (CNS) manifestations in our patient.Statement of Novelty: We herein report a novel set of compound heterozygous mutations in LRBA with atypical presentation of recurrent HLH with CNS manifestations, thus expanding the known phenotypic spectrum of LRBA deficiency.
- FREE ACCESSBackground: Eosinophilic gastrointestinal disease (EGID) is an umbrella term for a heterogeneous group of disorders affecting the GI tract. In contrast to the relatively common eosinophilic esophagitis (EoE), eosinophilic gastroenteritis (EGE) remains poorly understood in terms of both its pathophysiology and genetic etiology, while treatment options remain limited.Aim: To expand the genotypic spectrum of EGE and describe our long-term experience of treatment with ketotifen.Methods: Case report of a patient with EGE followed by our team for over 27 years.Results: Our patient was diagnosed with EGE at the age of 4 years, accompanied by multiple other atopic manifestations and serum eosinophilia. He was later diagnosed with a heterozygous variant in RUNX1, a gene implicated in multi-lineage hematopoiesis, inhibition of Th2 polarization and T regulatory cell function. The patient has experienced long-term symptom improvement while treated with the mast cell stabilizing H1 antihistamine, ketotifen, with substantial symptomatic worsening after this agent was briefly stopped.Conclusion: We expand the genotypic spectrum of EGID etiology to include mutations in RUNX1, and suggest ketotifen as a viable option for patients with treatment-refractory EGE.Statement of novelty: This case reports on a possible novel genetic cause of EGID and describes long-term successful clinical management with ketotifen.
- FREE ACCESS
- Laura Edith Abrego Fuentes,
- Jenny Garkaby,
- Jessica Willett Pachul,
- Abby Watts-Dickens,
- Meghan Fraser,
- Vy H.D. Kim, and
- Chaim M. Roifman
Background: Forkhead-box protein N1 (FOXN1) plays a critical role in the proper development and function of thymic epithelial cells, required for T cell ontogeny. Homozygous variants in the FOXN1 gene, encoding FOXN1, cause severe combined immunodeficiency (SCID), whereas heterozygous mutations are associated with variable presentations and over time, improving T cell function.Aim: To highlight the importance of broader genetic investigations to attain a definitive molecular diagnosis following abnormal newborn screening for SCID.Methods: Case report of a patient with immunodeficiency due to a novel de novo FOXN1 mutation.Results: The patient was identified following abnormal newborn screening for SCID in which T cell receptor excision circles were absent/very low. Initial immune investigations revealed severe T cell lymphopenia and poor lymphocyte function and she was diagnosed with T-B+NK+SCID. During work-up for hematopoietic stem cell transplantation, extensive genetic investigations identified a novel heterozygous mutation in FOXN1. A more conservative management approach was taken, and over the following months, the patient’s immune parameters improved.Conclusion: Newborn screening for SCID has facilitated the detection of SCID, as well as other T cell immunodeficiencies, before infectious complications and organ damage occur. Heterozygous mutations in FOXN1 are associated with more variable presentations including improving immune indices with age. Here, results of genetic investigations were essential for informing the management of this case.Statement of Novelty: We report a novel heterozygous mutation in FOXN1, presenting initially as T-B+NK+ SCID with gradual improvement of immune parameters over time. - OPEN ACCESSBackground: Recombination-activating gene 1 (RAG1) and recombination-activating gene 2 (RAG2) encode unique lymphocyte endonuclease proteins that are crucial in T and B cell development through V(D)J recombination. RAG1 gene defects lead to variable phenotypes, ranging from immunocompetent to severe combined immunodeficiency (SCID). Curative therapy for severe manifestations can be achieved through hematopoietic stem cell transplantation (HSCT). Advances in genomic sequencing have led to the discovery of new variants and it is recognized that the level of recombinase activity correlates with disease severity.Aim: To report the clinical presentation, immunological work-up, decision process to undergo HSCT, and confirmatory genetic diagnosis in a patient who was well until her initial presentation with disseminated vaccine-strain varicella.Methods: Clinical data was gathered through retrospective chart review. Immunological investigations, targeted gene sequencing, and thymic biopsy results were reviewed. Further genetic analysis, including whole exome and whole genome sequencing was performed.Results: Whole exome sequencing identified a single missense mutation in RAG1, R474C (c.1420C>T), which would not account for the clinical presentation. Healthy individuals with only 1 mutation have been reported. Subsequently, whole genome sequencing revealed a novel second heterozygous missense variant, H945D (c.2833G>T) in the RAG1 gene.Conclusion: Hypomorphic RAG1 mutations with residual activity have a diverse phenotypic expression. Identifying and understanding the implications of these mutations is crucial for disease prognostication and tailoring management.Statement of novelty: We present a novel RAG1 missense variant, with likely complete or partial loss of function, in a patient with significant impairment in cellular immunity.
- OPEN ACCESSIntroduction: Phosphatidylinositol-4,5-Bisphosphate 3-Kinase Catalytic Subunit Delta (PIK3CD) is one part of a heterodimer forming the enzyme phosphoinositide 3-kinase (PI3K), found primarily in leukocytes. PIK3CD generates phosphatidyl-inositol 3,4,5-trisphosphate (PIP3), and is involved in cell growth, survival, proliferation, motility, and morphology. An increasing number of patients have been described with heterozygous PIK3CD gain-of-function (GOF) mutations, leading to combined immunodeficiency with both B- and T-cell dysfunction. Patients suffer recurrent respiratory infections, often associated with bronchiectasis and ear and sinus damage, as well as severe recurrent or persistent infections by herpesviruses, including EBV-induced lymphoproliferation.Aim: To present the clinical phenotypic variability of a novel PI3KCD mutation within a family.Methods: Patient information was collected prospectively and retrospectively from medical records. Comprehensive immune work up, genetic, and signaling evaluation was performed.Results: We describe here 2 patients, daughter and mother, with heterozygous PIK3CD mutation identified by whole exome sequencing and Sanger confirmation. The child was screen-positive by newborn screening for severe combined immunodeficiency (SCID). Cellular assays revealed an increase in the baseline phosphorylation of T cells in the patient. Furthermore, both patients had hyper-activation of the catalytic domain, resulting in increased phosphorylation of AKT upon activation.Discussion: GOF mutations affecting the PIK3CD gene are associated with an increased risk for lymphoproliferation leading to Activated PIK3-delta syndrome (APDS). The clinical course of APDS is highly variable, ranging from combined immunodeficiency with recurrent infections, autoimmune complications, and requiring stem cell transplantation, through isolated antibody deficiency, to asymptomatic adults. Our patient is the first to be identified by newborn screening for SCID. Surprisingly, the clinical course has so far been unremarkable, as well, the mother appears to be completely asymptomatic. Nevertheless, the persistent lymphopenia indicates PIK3CD dysfunction. Because of the wide gap between laboratory findings and clinical manifestations, this kindred poses both a diagnostic as well treatment challenge.Statement of novelty: We report here a novel PIK3CD mutation diagnosed due to abnormal newborn screen for SCID.
- OPEN ACCESS
- Luis Murguia-Favela,
- Nigel Sharfe,
- Ariana Karanxha,
- Andrea Bates,
- Harjit Dadi,
- Lorand Cimpean, and
- Chaim M. Roifman
Background: CD40 deficiency is an autosomal recessive, combined primary immunodeficiency characterized by defects of immunoglobulin class switch recombination and somatic hypermutation. It is part of an expanding group of diseases collectively known as hyper immunoglobulin M syndromes. Clinical manifestations of the disease usually begin early in life with recurrent sinopulmonary bacterial infections and susceptibility to opportunistic organisms. Only 16 patients from 12 unrelated families have been reported to date, all with lack of membrane expression of CD40 molecule.Methods: Prospective and retrospective data was collected from the patient’s medical records, and Sanger sequencing, flow cytometry analysis, real-time polymerase chain reaction and western blotting were performed.Results: In contrast with the patients reported previously, our patient’s mutation permits CD40 expression on the cell membrane and adds 37 amino acids to the cytoplasmic domain of the protein. We predict this change to affect 1 of the 2 known TRAF2 binding sites, as well as generate defective internalization of the receptor, both of which are required processes for functional signaling by CD40.Conclusion: Our patient’s unique phenotype is an opportunity to further understand the biology and function of the CD40 receptor. As illustrated by this case, relying solely on flow cytometry for diagnosis of CD40 deficiency has the potential of overlooking patients with mutations that may allow residual protein expression. Therefore, confirmatory mutation analysis should always be performed.Statement of novelty: We report on a patient with a novel mutation in CD40 and a unique phenotype, characterized by a complete lack of CD40 function despite normal protein expression. To our knowledge, this has not been reported previously. The patient has a milder phenotype than described for other patients with CD40 deficiency. - OPEN ACCESSBackground: DNA ligase IV deficiency is a rare autosomal recessive condition resulting from mutations in LIG4, an essential component of the non-homologous end-joining pathway that prevents mutagenesis and apoptosis. Patients with LIG4 deficiency present with varying degrees of combined immunodeficiency, or less commonly, severe combined immunodeficiency (SCID). Assessment of thymus pathology has been instrumental in defining a growing number of T cell deficiencies. In this case report, we present thymic histopathology of a LIG4 deficient patient who presented with SCID.Methods: Whole exome sequencing and Sanger confirmation were used to identify a novel mutation in LIG4. Standard immune work up and histopathology were completed to characterize deficits in immune function and dysplastic thymic architecture in our patient.Results: Next generation sequencing techniques identified a homozygous c.1102G>T, resulting in amino acid change D368Y in the adenylation domain of LIG4. Histopathology revealed a distinct absence of Hassall’s corpuscles, lack of cortico-medullary demarcation, as well as lack of T cells and Langerhans histiocytes in the thymic medulla.Conclusion: We have identified a novel mutation in LIG4 resulting in a SCID phenotype. Underdevelopment of the thymus, characterized by a lack of Hassall’s corpuscles and competent thymocytes, likely contributes to the immune defects observed in patients with mutations in LIG4.Statement of novelty: We report here a novel mutation in LIG4 as well as the first description of detailed thymus pathology in this condition.
