Isabelle Melki

Mutation in the SLC29A3 Gene: A New Cause of a Monogenic, Autoinflammatory Condition

Germline mutations in the SLC29A3 gene result in a range of recessive, clinically related syndromes: H syndrome, pigmented hypertrichosis with insulin-dependent diabetes mellitus syndrome, Faisalabad histiocytosis, and sinus histiocytosis with massive lymphadenopathy. The main symptoms of these diseases are hyperpigmentation with hypertrichosis, sensorineural deafness, diabetes, short stature, uveitis, and Rosai-Dorfman like histiocytosis. Here, we report the case of an 11-month-old boy with early-onset, recurrent episodes of unprovoked fever lasting 7 to 10 days and associated with pericardial effusion, abdominal pain, diarrhea, and inflammation. Physical examination revealed hyperpigmentation with hypertrichosis, dysmorphic features, and spleen and liver enlargement. Failure to thrive, sensorineural deafness, retarded psychomotor development, and a Rosai-Dorfman like cheek lesion developed subsequently. The febrile episodes did not respond to tumor necrosis factor α antagonists and interleukin-1. Sequencing of the SLC29A3 gene revealed a homozygous missense mutation c.1088G>A (p.Arg363Gln). These observations suggest that a newly identified mutation in the SLC29A3 gene may be associated with an autoinflammatory disorder. Genetic defects in SLC29A3 should be considered in patients with autoinflammatory manifestations, recurrent febrile attacks, and 1 or more of the symptoms found in the broad spectrum of SLC29A3-related disorders (especially hyperpigmentation with hypertrichosis).

Disease-associated mutations identify a novel region in human STING necessary for the control of type I interferon signaling

Background Gain‐of‐function mutations in transmembrane protein 173 (TMEM173) encoding stimulator of interferon genes (STING) underlie a recently described type I interferonopathy called STING‐associated vasculopathy with onset in infancy (SAVI). Objectives We sought to define the molecular and cellular pathology relating to 3 individuals variably exhibiting the core features of the SAVI phenotype including systemic inflammation, destructive skin lesions, and interstitial lung disease. Methods Genetic analysis, conformational studies, in vitro assays and ex vivo flow‐cytometry were performed. Results Molecular and in vitro data demonstrate that the pathology in these patients is due to amino acid substitutions at positions 206, 281, and 284 of the human STING protein. These mutations confer cGAMP‐independent constitutive activation of type I interferon signaling through TBK1 (TANK‐binding kinase), independent from the alternative STING pathway triggered by membrane fusion of enveloped RNA viruses. This constitutive activation was abrogated by ex vivo treatment with the janus kinase 1/2 inhibitor ruxolitinib. Conclusions Structural analysis indicates that the 3 disease‐associated mutations at positions 206, 281, and 284 of the STING protein define a novel cluster of amino acids with functional importance in the regulation of type I interferon signaling.

Assessment of Type I Interferon Signaling in Pediatric Inflammatory Disease

PurposeIncreased type I interferon is considered relevant to the pathology of a number of monogenic and complex disorders spanning pediatric rheumatology, neurology, and dermatology. However, no test exists in routine clinical practice to identify enhanced interferon signaling, thus limiting the ability to diagnose and monitor treatment of these diseases. Here, we set out to investigate the use of an assay measuring the expression of a panel of interferon-stimulated genes (ISGs) in children affected by a range of inflammatory diseases.Design, Setting, and ParticipantsA cohort study was conducted between 2011 and 2016 at the University of Manchester, UK, and the Institut Imagine, Paris, France. RNA PAXgene blood samples and clinical data were collected from controls and symptomatic patients with a genetically confirmed or clinically well-defined inflammatory phenotype. The expression of six ISGs was measured by quantitative polymerase chain reaction, and the median fold change was used to calculate an interferon score (IS) for each subject compared to a previously derived panel of 29 controls (where +2 SD of the control data, an IS of >2.466, is considered as abnormal). Results were correlated with genetic and clinical data.ResultsNine hundred ninety-two samples were analyzed from 630 individuals comprising symptomatic patients across 24 inflammatory genotypes/phenotypes, unaffected heterozygous carriers, and controls. A consistent upregulation of ISG expression was seen in 13 monogenic conditions (455 samples, 265 patients; median IS 10.73, interquartile range (IQR) 5.90–18.41), juvenile systemic lupus erythematosus (78 samples, 55 patients; median IS 10.60, IQR 3.99–17.27), and juvenile dermatomyositis (101 samples, 59 patients; median IS 9.02, IQR 2.51–21.73) compared to controls (78 samples, 65 subjects; median IS 0.688, IQR 0.427–1.196), heterozygous mutation carriers (89 samples, 76 subjects; median IS 0.862, IQR 0.493–1.942), and individuals with non-molecularly defined autoinflammation (89 samples, 69 patients; median IS 1.07, IQR 0.491–3.74).Conclusions and RelevanceAn assessment of six ISGs can be used to define a spectrum of inflammatory diseases related to enhanced type I interferon signaling. If future studies demonstrate that the IS is a reactive biomarker, this measure may prove useful both in the diagnosis and the assessment of treatment efficacy.

Biological treatment in systemic juvenile idiopathic arthritis: achievement of inactive disease or clinical remission on a first, second or third biological agent.

Objectives To analyse the effect of biological agents (BAs) in terms of achieving inactive disease (ID) or clinical remission (CR) in patients with systemic juvenile idiopathic arthritis (SJIA), to describe effects of switching or discontinuing a BA and to assess the proportion of patients able to maintain ID or CR off steroids and after withdrawing BA therapy. Methods Retrospective study in a French paediatric rheumatology reference centre using the CEMARA (CEntre des MAladies RAres) register. Results Seventy-seven patients were included with a cumulative follow-up of 245.5 patient-years (median 1.1, range 0.5–8.0). On a first BA, ID was achieved in 37 patients, including 1 patient out of 12 patients on etanercept, 26 patients out of 51 on anakinra and 7 out of 10 on canakinumab. One patient on abatacept and two patients on tocilizumab also achieved ID. Switching of BA was common. The switch to a second (n=34), third (n=18) or fourth (n=4) BA resulted in ID in a further 13 patients, either on canakinumab (n=6) or tocilizumab (n=7). At last follow-up, 40 patients were in CR (27 patients off steroids, 5 patients having never received steroid treatment), either on (n=29) or off (n=11) BA. Conclusions In this series of patients with SJIA, interleukin-1 inhibitors were associated with a higher proportion of ID than tumour necrosis factor inhibitors when used as first BA. Switching allowed some patients to achieve ID when treated with canakinumab or tocilizumab. CR was eventually achieved in more than half of the patients.

Effect of Biologic Treatments on Growth in Children with Juvenile Idiopathic Arthritis

Objective. Growth retardation is a frequent complication of severe juvenile idiopathic arthritis (JIA). Biologic treatments may improve growth velocity by controlling systemic inflammation and reducing corticosteroids. Our goals were to compare growth velocity before and after the onset of biologic therapy and to determine whether the JIA subtype, the use of steroids, the requirement of one or several biologic agents, or the disease activity influenced growth velocity. Methods. We retrospectively analyzed the growth of children with JIA who never received growth hormone treatment, who started biologic treatment before puberty, and who were followed for at least 6 months afterward. Results. We included 100 children (33 boys). Median patient age was 7.1 years (range: 1.6–15.7) at the onset of biologic treatment and 11.0 years (range: 2.3–19.5) at the latest followup. Forty-six patients had received corticosteroid and 34 had received more than 1 biologic agent. Patient median height expressed as SD score (SDS) was 0.31 (range: −2.47 to 5.46) at disease onset, −0.24 (−3.63 to 2.90) at biologic therapy onset (p < 0.0001), and −0.15 (−4.95 to 3.52) at the latest followup (p = 0.171 compared to biologic treatment onset). Patients who required several biologics and systemic patients had a significantly lower growth velocity after the onset of biologic treatment. At the latest followup, 18% of our study group had low growth velocities and 19% were below −2SD or shorter than genetically programmed. Conclusion. In a subset of patients, particularly systemic JIA patients and patients who required more than 1 biologic, biologic therapy may be insufficient to restore normal growth velocity.

Novel monogenic diseases causing human autoimmunity.

Fuelled by the on-going sequencing revolution, the last two years have seen a number of exciting discoveries relating to monogenic disorders predisposing to autoimmunity that provide new insights into the function of the human immune system. Here we discuss a selection of these diseases due to mutations in PRKCD, CTLA4, STAT3, IFIH1, TMEM173 and COPA.

Brief Report: Blockade of TANK-Binding Kinase 1/IKKɛ Inhibits Mutant Stimulator of Interferon Genes (STING)–Mediated Inflammatory Responses in Human Peripheral Blood Mononuclear Cells

Gain‐of‐function mutations in TMEM173, encoding the stimulator of interferon (IFN) genes (STING) protein, underlie a novel type I interferonopathy that is minimally responsive to conventional immunosuppressive therapies and associated with high frequency of childhood morbidity and mortality. STING gain‐of‐function causes constitutive oversecretion of IFN. This study was undertaken to determine the effects of a TANK‐binding kinase 1 (TBK‐1)/IKKɛ inhibitor (BX795) on secretion and signaling of IFN in primary peripheral blood mononuclear cells (PBMCs) from patients with mutations in STING.

A decision tree for the genetic diagnosis of deficiency of adenosine deaminase 2 (DADA2): a French reference centres experience

Deficiency of adenosine deaminase 2 (DADA2) is a recently described autoinflammatory disorder. Genetic analysis is required to confirm the diagnosis. We aimed to describe the identifying symptoms and genotypes of patients referred to our reference centres and to improve the indications for genetic testing. DNA from 66 patients with clinically suspected DADA2 were sequenced by Sanger or next-generation sequencing. Detailed epidemiological, clinical and biological features were collected by use of a questionnaire and were compared between patients with and without genetic confirmation of DADA2. We identified 13 patients (19.6%) carrying recessively inherited mutations in ADA2 that were predicted to be deleterious. Eight patients were compound heterozygous for mutations. Seven mutations were novel (4 missense variants, 2 predicted to affect mRNA splicing and 1 frameshift). The mean age of the 13 patients with genetic confirmation was 12.7 years at disease onset and 20.8 years at diagnosis. Phenotypic manifestations included fever (85%), vasculitis (85%) and neurological disorders (54%). Features best associated with a confirmatory genotype included fever with neurologic or cutaneous attacks (odds ratio [OR] 10.71, p = 0.003 and OR 10.9, p < 0.001), fever alone (OR 8.1, p = 0.01), and elevated C-reactive protein (CRP) level with neurologic involvement (OR 6.63, p = 0.017). Our proposed decision tree may help improve obtaining genetic confirmation of DADA2 in the context of autoinflammatory symptoms. Prerequisites for quick and low-cost Sanger analysis include one typical cutaneous or neurological sign, one marker of inflammation (fever or elevated CRP level), and recurrent or chronic attacks in adults.

TBK1 / IKKE blockade inhibits mutant STING mediated inflammatory response in patient cells

Gain‐of‐function mutations in TMEM173, encoding the stimulator of interferon (IFN) genes (STING) protein, underlie a novel type I interferonopathy that is minimally responsive to conventional immunosuppressive therapies and associated with high frequency of childhood morbidity and mortality. STING gain‐of‐function causes constitutive oversecretion of IFN. This study was undertaken to determine the effects of a TANK‐binding kinase 1 (TBK‐1)/IKKɛ inhibitor (BX795) on secretion and signaling of IFN in primary peripheral blood mononuclear cells (PBMCs) from patients with mutations in STING.

Musculoskeletal Disease in MDA5-Related Type I Interferonopathy: A Mendelian Mimic of Jaccoud's Arthropathy

To define the molecular basis of a multisystem phenotype with progressive musculoskeletal disease of the hands and feet, including camptodactyly, subluxation, and tendon rupture, reminiscent of Jaccouds arthropathy.