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| [Paper Type: Novel mutation and VUS] AND [Author: Upton, Julia] (4) | 26 Mar 2025 |
| [Paper Type: Novel mutation and VUS] AND [Author: Dadi, Harjit] (4) | 26 Mar 2025 |
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- OPEN ACCESS
- Laura Abrego Fuentes,
- Jenny Garkaby,
- Ori Scott,
- Jessica Willet Pachul,
- Harjit Dadi,
- Daniele Merico, and
- Linda Vong
Introduction: The phosphoinositide 3-kinase (PI3K) pathway plays critical roles in diverse cellular processes, including differentiation, proliferation, motility, survival, and growth. PI3Kδ, comprised of the catalytic subunit p110δ and regulatory subunit p85α, is essential for normal lymphocyte and myeloid development and function. Gain-of-function mutations in PIK3CD (encoding p110δ) cause a combined immunodeficiency known as activated PI3Kδ syndrome (APDS), in which patients frequently present with recurrent respiratory infections, severe recurrent (or persistent) infections with herpes family viruses, and lymphadenopathy.Aim: To describe the clinical presentation, immune evaluation, and genetic work-up of 2 patients (daughter and mother) with recurrent sinopulmonary, soft tissue, and skin infections.Results: Both daughter and mother presented with recurrent sinopulmonary and soft tissue infections. Immune evaluation of the daughter revealed intermittent hypogammaglobulinemia and abnormal specific vaccine responses, while immune parameters of her mother were normal. Whole exome sequencing identified a novel mutation in PIK3CD (NM_005026), c.C719T, resulting in p.T240M. Western blot analysis of downstream AKT levels revealed increased basal phosphorylation, in line with gain-of-function mutations of PIK3CD.Conclusion: The novel missense mutation in PIK3CD occurs in the region encoding the Ras-binding domain (RBD) of p110δ, and likely alters the structural configuration of the domain. To date, pathogenic mutations targeting the RBD of p110δ have not yet been described. Our results expand on the genotypic spectrum of APDS.Statement of Novelty: We describe a novel mutation in the Ras-binding domain of PIK3CD leading to a presentation of recurrent sinopulmonary and soft tissue infections in the context of APDS. - 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.
