Immunophenotyping of A20 haploinsufficiency by multicolor flow cytometry.

Haploinsufficiency of A20 (HA20) causes inflammatory disease resembling Behçet's disease; many cases have been reported, including some that are complicated with autoimmune diseases. This study aims to clarify the immunophenotype of patients with HA20 by analyzing lymphocyte subsets using multicolor flow cytometry. The patients with HA20 previously diagnosed in a nationwide survey were compared by their cell subpopulations. In total, 27 parameters including regulatory T cells (Tregs), double-negative T cells (DNTs), and follicular helper T cells (TFHs) were analyzed and compared with the reference values in four age groups: 0-1, 2-6, 7-19, and ≥20 years. The Tregs of patients with HA20 tended to increase in tandem with age-matched controls at all ages. In addition, patients ≥20 years had increased DNTs compared with controls, whereas TFHs significantly increased in younger patients. In HA20 patients, the increase in DNTs and TFHs may contribute to the development of autoimmune diseases.

A20 Haploinsufficiency in East Asia.

A20, encoded by the TNFAIP3 gene, is a negative regulator of tumor necrosis factor (TNF)-nuclear factor-κB signaling. It was recently demonstrated that A20 haploinsufficiency (HA20), caused by a heterozygous mutation in the TNFAIP3 gene, can present as an early onset autoinflammatory disease resembling Behçet's disease (BD). In addition to autoinflammatory symptoms, HA20 was also reported to be associated with autoimmune diseases and immunodeficiency. Because the phenotypes associated with HA20 are broad, with different severities observed even among individuals in the same family with identical mutations, it has been assumed that the symptoms of HA20 may depend on genetic background and environmental factors. In this review, we summarize the characteristics of patients with HA20 in East Asia and compare these with patients in other regions, mainly the USA and Europe. Patients with HA20 in East Asia developed recurrent fever more frequently than patients in other regions, but were less likely to develop typical BD symptoms such as skin rashes and genital ulcers. In addition, patients with HA20 in East Asia had low rates of complication with autoimmune diseases and low autoantibody detection rates. While anti-TNF-α agents were the primary treatments for severe HA20 in East Asia, anti-interleukin-1 agents and Janus kinase inhibitors were also administered in other regions. Future studies will need to establish methods for analyzing the pathophysiology of HA20 and determining optimal treatment strategies for each patient.

Primary Immunodeficiency Disease Mimicking Pediatric Bechet's Disease.

Behcet's disease (BD) is a chronic inflammatory disease with multisystemic involvement. Its etiology is considered to involve complex environmental and genetic factors. Several susceptibility genes for BD, such as human leukocyte antigen (HLA)-A26, IL23R-IL12RB2, IL10 and ERAP1, in addition to the well-studied HLA-B51, were mainly identified by genome-wide association studies. A heterozygous mutation in TNFAIP3, which leads to A20 haploinsufficiency, was found to cause an early-onset autoinflammatory disease resembling BD in 2016. Several monogenic diseases associated with primary immunodeficiency disease and trisomy 8 have recently been reported to display BD-like phenotypes. Among the genes causing these diseases, TNFAIP3, NEMO, RELA, NFKB1 and TNFRSF1A are involved in the NF-κB (nuclear factor κ light-chain enhancer of activated B cells) signaling pathway, indicating that this pathway plays an important role in the pathogenesis of BD. Because appropriate treatment may vary depending on the disease, analyzing the genetic background of patients with such diseases is expected to help elucidate the etiology of pediatric BD and assist with its treatment. Here, we summarize recently emerging knowledge about genetic predisposition to BD.

Functional analysis of novel A20 variants in patients with atypical inflammatory diseases.

BACKGROUND: A20 haploinsufficiency (HA20) is an early-onset autoinflammatory disease caused by mutations in the TNFAIP3 gene, which encodes the protein A20. Numerous truncating mutations in the TNFAIP3 gene have been reported in HA20 patients, whereas fewer missense variants have had their pathogenicity confirmed. Here, we evaluated the pathogenic significance of three previously unreported missense variants of the TNFAIP3 gene in suspected cases of HA20. METHODS: We obtained the clinical features and immunological data of three patients with missense variants (Glu192Lys, Ile310Thr, and Gln709Arg) of unknown significance of TNFAIP3. We then performed in vitro functional assays including analysis of nuclear factor (NF)-κB reporter gene activity, detection of A20 expression and phosphorylation of A20 by IκB kinase ß (IKKß), and K63-deubiquitination assay using TNFAIP3-deficient HEK293 cells. Three known pathogenic missense mutations reported previously were also investigated. RESULTS: The inhibitory effect on NF-κB reporter gene activity was significantly disrupted by A20 Glu192Lys and the three known mutations. The variants Ile310Thr and Gln709Arg did not show a difference from the wild type in any of the assays performed in this study. CONCLUSIONS: Among the three variants in the TNFAIP3 gene, Glu192Lys was interpreted as being likely pathogenic, but Ile310Thr and Gln709Arg as being not pathogenic (uncertain significance and likely benign, respectively), based on the American College of Medical Genetics and Genomics standards and guidelines. Our study highlights the necessity of performing in vitro functional assays, notably, NF-κB reporter gene assay, to evaluate the pathogenicity of TNFAIP3 missense variants for the accurate diagnosis of HA20.

Dysregulation of the Intestinal Microbiome in Patients With Haploinsufficiency of A20.

INTRODUCTION: Haploinsufficiency of A20 (HA20) is a form of inborn errors of immunity (IEI). IEIs are genetically occurring diseases, some of which cause intestinal dysbiosis. Due to the dysregulation of regulatory T cells (Tregs) observed in patients with HA20, gut dysbiosis was associated with Tregs in intestinal lamina propria. METHODS: Stool samples were obtained from 16 patients with HA20 and 15 of their family members. Infant samples and/or samples with recent antibiotics use were excluded; hence, 26 samples from 13 patients and 13 family members were analyzed. The 16S sequencing process was conducted to assess the microbial composition of samples. Combined with clinical information, the relationship between the microbiome and the disease activity was statistically analyzed. RESULTS: The composition of gut microbiota in patients with HA20 was disturbed compared with that in healthy family members. Age, disease severity, and use of immunosuppressants corresponded to dysbiosis. However, other explanatory factors, such as abdominal symptoms and probiotic treatment, were not associated. The overall composition at the phylum level was stable, but some genera were significantly increased or decreased. Furthermore, among the seven operational taxonomic units (OTUs) that increased, two OTUs, Streptococcus mutans and Lactobacillus salivarius, considerably increased in patients with autoantibodies than those without autoantibodies. DISCUSSION: Detailed interaction on intestinal epithelium remains unknown; the relationship between the disease and stool composition change helps us understand the mechanism of an immunological reaction to microorganisms.

Myelodysplastic syndromes in a pediatric patient with Cri du Chat syndrome with a ring chromosome 5.

Few hematological complications have previously been reported in association with Cri du Chat syndrome (CdCS). A case of myelodysplastic syndromes (MDS) in a pediatric patient with CdCS is herein presented. A 17-year-old female with CdCS caused by ring chromosome 5 was admitted to the hospital for investigation of a 1-month history of anemia. Based on the morphological findings of bone marrow, the patient was diagnosed with refractory cytopenia with multilineage dysplasia. The risk group was classified as intermediate-1 in the International Prognostic Scoring System (IPSS), and low in the revised IPSS. Assessment by microarray comparative genomic hybridization (CGH) identified the breakpoints of ring chromosome 5 as 46,XX,r(5)(p14.3q35.3). This revealed that the 5q terminal deletion did not include the common deleted region of MDS with del(5q). Treatment with azacitidine was initiated to control disease progression and improve quality of life. At baseline, the patient had a mean transfusion requirement of 3 units/month, which decreased to 2 units/month after six cycles of azacitidine and to 1 unit/month after 10 cycles of azacitidine. Cytopenia observed in the presented case seemed irrelevant to ring chromosome 5 which is the causative cytogenetic abnormality of CdCS, and further analyses may be needed to clarify the pathogenesis.

Autosomal dominant Hashimoto's thyroiditis with a mutation in TNFAIP3.

Hashimoto's thyroiditis (HT) is an autoimmune disease thought to involve a combination of genetic and environmental factors, but its detailed pathogenesis is unknown. We present a family with haploinsufficiency of the gene encoding tumor necrosis factor α-induced protein 3 (TNFAIP3, also known as A20) and show a link with HT in a three-generation pedigree. Currently, TNFAIP3 polymorphisms are associated with several autoimmune diseases, and haploinsufficiency of A20 was recently observed in families with an early-onset autoinflammatory disease resembling Behçet's disease. However, HT has not been linked with TNFAIP3 variants. We analyzed TNFAIP3 and human leukocyte antigen (HLA) in the family showing HT as an autosomal dominant trait, and identified a novel heterozygous c.2209delC mutation of TNFAIP3 in the members with HT. The known HLA haplotypes linked to HT could not be identified. Based on our analysis of this pedigree, we consider HT as a possible phenotype of A20 haploinsufficiency.