Tsubasa Okano

Phosphatase and tensin homolog (PTEN) mutation can cause activated phosphatidylinositol 3-kinase δ syndrome–like immunodeficiency

BACKGROUND Activated phosphatidylinositol 3-kinase δ syndrome (APDS) is a recently discovered primary immunodeficiency disease (PID). Excess phosphatidylinositol 3-kinase (PI3K) activity linked to mutations in 2 PI3K genes, PIK3CD and PIK3R1, causes APDS through hyperphosphorylation of AKT, mammalian target of rapamycin (mTOR), and S6. OBJECTIVE This study aimed to identify novel genes responsible for APDS. METHODS Whole-exome sequencing was performed in Japanese patients with PIDs. Immunophenotype was assessed through flow cytometry. Hyperphosphorylation of AKT, mTOR, and S6 in lymphocytes was examined through immunoblotting, flow cytometry, and multiplex assays. RESULTS We identified heterozygous mutations of phosphatase and tensin homolog (PTEN) in patients with PIDs. Immunoblotting and quantitative PCR analyses indicated that PTEN expression was decreased in these patients. Patients with PTEN mutations and those with PIK3CD mutations, including a novel E525A mutation, were further analyzed. The clinical symptoms and immunologic defects of patients with PTEN mutations, including lymphocytic AKT, mTOR, and S6 hyperphosphorylation, resemble those of patients with APDS. Because PTEN is known to suppress the PI3K pathway, it is likely that defective PTEN results in activation of the PI3K pathway. CONCLUSION PTEN loss-of-function mutations can cause APDS-like immunodeficiency because of aberrant PI3K pathway activation in lymphocytes.

Haploinsufficiency of TNFAIP3 (A20) by germline mutation is involved in autoimmune lymphoproliferative syndrome

Background Autoimmune diseases in children are rare and can be difficult to diagnose. Autoimmune lymphoproliferative syndrome (ALPS) is a well‐characterized pediatric autoimmune disease caused by mutations in genes associated with the FAS‐dependent apoptosis pathway. In addition, various genetic alterations are associated with the ALPS‐like phenotype. Objective The aim of the present study was to elucidate the genetic cause of the ALPS‐like phenotype. Methods Candidate genes associated with the ALPS‐like phenotype were screened by using whole‐exome sequencing. The functional effect of the identified mutations was examined by analyzing the activity of related signaling pathways. Results A de novo heterozygous frameshift mutation of TNF‐&agr;–induced protein 3 (TNFAIP3, A20), a negative regulator of the nuclear factor &kgr;B pathway, was identified in one of the patients exhibiting the ALPS‐like phenotype. Increased activity of the nuclear factor &kgr;B pathway was associated with haploinsufficiency of TNFAIP3 (A20). Conclusion Haploinsufficiency of TNFAIP3 (A20) by a germline heterozygous mutation leads to the ALPS phenotype.

Hematopoietic Stem Cell Transplantation for XIAP Deficiency in Japan

BackgroundX-linked inhibitor of apoptosis protein (XIAP) deficiency is a rare immunodeficiency that is characterized by recurrent hemophagocytic lymphohistiocytosis (HLH) and splenomegaly and sometimes associated with refractory inflammatory bowel disease (IBD). Although hematopoietic stem cell transplantation (HSCT) is the only curative therapy, the outcomes of HSCT for XIAP deficiency remain unsatisfactory compared with those for SLAM-associated protein deficiency and familial HLH.AimTo investigate the outcomes and adverse events of HSCT for patients with XIAP deficiency, a national survey was conducted.MethodsA spreadsheet questionnaire was sent to physicians who had provided HSCT treatment for patients with XIAP deficiency in Japan.ResultsUp to the end of September 2016, 10 patients with XIAP deficiency had undergone HSCT in Japan, 9 of whom (90%) had survived. All surviving patients had received a fludarabine-based reduced intensity conditioning (RIC) regimen. Although 5 patients developed post-HSCT HLH, 4 of them survived after etoposide administration. In addition, the IBD associated with XIAP deficiency improved remarkably after HSCT in all affected cases.ConclusionThe RIC regimen and HLH control might be important factors for successful HSCT outcomes, with improved IBD, in patients with XIAP deficiency.

Hematopoietic stem cell transplantation in 29 patients hemizygous for hypomorphic IKBKG/NEMO mutations

X-linked recessive ectodermal dysplasia with immunodeficiency is a rare primary immunodeficiency caused by hypomorphic mutations of the IKBKG gene encoding the nuclear factor κB essential modulator (NEMO) protein. This condition displays enormous allelic, immunological, and clinical heterogeneity, and therapeutic decisions are difficult because NEMO operates in both hematopoietic and nonhematopoietic cells. Hematopoietic stem cell transplantation (HSCT) is potentially life-saving, but the small number of case reports available suggests it has been reserved for only the most severe cases. Here, we report the health status before HSCT, transplantation outcome, and clinical follow-up for a series of 29 patients from unrelated kindreds from 11 countries. Between them, these patients carry 23 different hypomorphic IKBKG mutations. HSCT was performed from HLA-identical related donors (n = 7), HLA-matched unrelated donors (n = 12), HLA-mismatched unrelated donors (n = 8), and HLA-haploidentical related donors (n = 2). Engraftment was documented in 24 patients, and graft-versus-host disease in 13 patients. Up to 7 patients died 0.2 to 12 months after HSCT. The global survival rate after HSCT among NEMO-deficient children was 74% at a median follow-up after HSCT of 57 months (range, 4-108 months). Preexisting mycobacterial infection and colitis were associated with poor HSCT outcome. The underlying mutation does not appear to have any influence, as patients with the same mutation had different outcomes. Transplantation did not appear to cure colitis, possibly as a result of cell-intrinsic disorders of the epithelial barrier. Overall, HSCT can cure most clinical features of patients with a variety of IKBKG mutations.

Flow cytometry-based diagnosis of primary immunodeficiency diseases

Primary immunodeficiencies (PIDs) are a heterogeneous group of inherited diseases of the immune system. The definite diagnosis of PID is ascertained by genetic analysis; however, this takes time and is costly. Flow cytometry provides a rapid and highly sensitive tool for diagnosis of PIDs. Flow cytometry can evaluate specific cell populations and subpopulations, cell surface, intracellular and intranuclear proteins, biologic effects associated with specific immune defects, and certain functional immune characteristics, each being useful for the diagnosis and evaluation of PIDs. Flow cytometry effectively identifies major forms of PIDs, including severe combined immunodeficiency, X-linked agammaglobulinemia, hyper IgM syndromes, Wiskott-Aldrich syndrome, X-linked lymphoproliferative syndrome, familial hemophagocytic lymphohistiocytosis, autoimmune lymphoproliferative syndrome, IPEX syndrome, CTLA 4 haploinsufficiency and LRBA deficiency, IRAK4 and MyD88 deficiencies, Mendelian susceptibility to mycobacterial disease, chronic mucocuneous candidiasis, and chronic granulomatous disease. While genetic analysis is the definitive approach to establish specific diagnoses of PIDs, flow cytometry provides a tool to effectively evaluate patients with PIDs at relatively low cost.

Multicolor Flow Cytometry for the Diagnosis of Primary Immunodeficiency Diseases

PurposePrimary immunodeficiency diseases (PIDDs) are rare inherited diseases that impair the human immune system. We established a multicolor flow cytometric assay to comprehensively evaluate the immune status and immunological characteristics of patients with PIDDs.MethodsFifty-nine normal controls and 75 patients with PIDDs, including X-linked severe combined immunodeficiency (X-SCID), X-linked agammaglobulinemia (XLA), X-linked hyper IgM syndrome (X-HIGM), ataxia telangiectasia (AT), Wiskott-Aldrich syndrome (WAS), hyper IgE syndrome (HIES), and chronic mucocutaneous candidiasis disease (CMCD), were enrolled in this study. Immunophenotyes were evaluated by multicolor flow cytometry using seven different panels that allowed the detection of major leukocyte populations in peripheral blood.ResultsMulticolor flow cytometry revealed distinct leukocyte populations and immunological features of patients with X-SCID, XLA, X-HIGM, AT, WAS, HIES, and CMCD.ConclusionsImmunophenotyping by multicolor flow cytometry is useful to evaluate immune status and contributes to the diagnosis and management of patients with PIDDs.

Novel compound heterozygous mutations in a Japanese girl with Janus kinase 3 deficiency.

Severe combined immunodeficiency (SCID) is the most severe form of primary immunodeficiency disease, and it is characterized by marked impairment in cellular and humoral immunity. Mutations in several genes cause SCID, one of which is Janus kinase 3 (JAK3), resulting in autosomal recessive T(–)B(+)NK(–) SCID. Only three patients with JAK3‐deficient SCID have been reported in Japan. We herein describe the case of a 6‐month‐old girl with pneumocystis pneumonia, who was diagnosed with SCID with compound heterozygous JAK3 mutations (c.1568G>A + c.421‐10G>A). One of the mutations was previously reported in another Japanese patient. The other mutation was a novel and de novo relatively deep intronic mutation causing aberrant RNA splicing. The patient was successfully treated with bone marrow transplantation from a haploidentical donor.

Recurrent Acute Abdomen as the Main Manifestation of Hereditary Angioedema

A diagnosis of hereditary angioedema is usually made with recurrent episodes of swelling of the subcutaneous tissue with a family history. We herein report a case in which recurrent acute abdomen was the main manifestation of hereditary angioedema. A 45-year-old womon presented with a 10-year history of recurrent severe abdominal pain. Abdominal computed tomography revealed remarkable submucosal edema of the ileum. A blood examination revealed grossly reduced complement C4 and CH50 with deficiency of C1-inhibitor. Genetic testing revealed a heterozygous nonsense mutation of the SERPING1 gene, and a diagnosis of hereditary angioedema was made. Hereditary angioedema should be listed as a differential diagnosis of recurrent acute abdomen.

Dysregulation of Epstein-Barr Virus Infection in Hypomorphic ZAP70 Mutation

Background Some patients with genetic defects develop Epstein-Barr virus (EBV)-associated lymphoproliferative disorder (LPD)/lymphoma as the main feature. Hypomophic mutations can cause different clinical and laboratory manifestations from null mutations in the same genes. Methods We sought to describe the clinical and immunologic phenotype of a 21-month-old boy with EBV-associated LPD who was in good health until then. A genetic and immunologic analysis was performed. Results Whole-exome sequencing identified a novel compound heterozygous mutation of ZAP70 c.703-1G>A and c.1674G>A. A small amount of the normal transcript was observed. Unlike ZAP70 deficiency, which has been previously described as severe combined immunodeficiency with nonfunctional CD4+ T cells and absent CD8+ T cells, the patient had slightly low numbers of CD8+ T cells and a small amount of functional T cells. EBV-specific CD8+ T cells and invariant natural killer T (iNKT) cells were absent. The T-cell receptor repertoire, determined using next generation sequencing, was significantly restricted. Conclusions Our patient showed that a hypomorphic mutation of ZAP70 can lead to EBV-associated LPD and that EBV-specific CD8+ T cells and iNKT cells are critically involved in immune response against EBV infection.

Hematopoietic stem cell transplantation for progressive combined immunodeficiency and lymphoproliferation in patients with activated phosphatidylinositol-3-OH kinase δ syndrome type 1

Background: Activated phosphatidylinositol‐3‐OH kinase &dgr; syndrome type 1 (APDS1) is a recently described primary immunodeficiency syndrome characterized by recurrent respiratory tract infections, lymphoid hyperplasia, and Herpesviridae infections caused by germline gain‐of‐function mutations of PIK3CD. Hematopoietic stem cell transplantation (HSCT) can be considered to ameliorate progressive immunodeficiency and associated malignancy, but appropriate indications, methods, and outcomes of HSCT for APDS1 remain undefined. Objective: Our objective was to analyze the clinical manifestations, laboratory findings, prognosis, and treatment of APDS1 and explore appropriate indications and methods of HSCT. Methods: We reviewed retrospectively the medical records of cohorts undergoing HSCT at collaborating facilities. Results: Thirty‐year overall survival was 86.1%, but event‐free survival was 39.6%. Life‐threatening events, such as severe infections or lymphoproliferation, were frequent in childhood and adolescence and were common indications for HSCT. Nine patients underwent HSCT with fludarabine‐based reduced‐intensity conditioning. Seven patients survived after frequent adverse complications and engraftment failure. Most symptoms improved after HSCT. Conclusion: Patients with APDS1 showed variable clinical manifestations. Life‐threatening progressive combined immunodeficiency and massive lymphoproliferation were common indications for HSCT. Fludarabine‐based reduced‐intensity conditioning–HSCT ameliorated clinical symptoms, but transplantation‐related complications were frequent, including graft failure. GRAPHICAL ABSTRACT Figure. No caption available.