Novel gain-of-function mutation in STAT1 protein with ALPS-like presentation

A comparative description of dysregulatory syndromes with mutations in signal transducer and activator of transcription (STAT) genes. STAT 1, 3 and 5b loss of function (LOF) and gain of function (GOF) mutations are a heterogeneous group of genetic disorders that range from immunodeficiency (ID) to autoimmune disease (AID), depending on the underlying signalling pathway defect. Between them, there are clear overlapping and differences in clinical presentation and laboratory findings. Dysregulatory syndromes due to LOF and GOF mutations in STAT1, 3 and 5b are a particular group of primary immunodeficiencies (PIDs) in which AID may be the predominant finding in addition to infections susceptibility. STAT1 GOF mutations were described as the major cause of chronic mucocutaneous candidiasis, while activating STAT3 mutations result in early-onset multiorgan autoimmunity and ID. Human STAT5b deficiency is a rare disease that also involves ID and severe growth failure. In recent years, the identification of the genes involved in these disorders allowed to differentiate these overlapping syndromes in order to choose the most effective therapeutic options.

Purpose: STAT1 mutations leading to a gain-of-function (GOF) are the first cause of Chronic Mucocutaneous Candidiasis (CMC). We describe a patient presenting a new GOF mutation in STAT1 with clinical symptoms consisting of CMC, recurrent pneumoniae and flowering rosacea with ocular involvement in relation to chronic demodicosis. Methods: A genetic analysis by targeted Next Generation Sequencing (DIPAI v.1) exploring the 98 genes most frequently involved in primary immunodeficiencies including STAT1 was performed to identify new mutations underlying STAT1 GOF. Results: NGS (DIPAI panel) identify a new missense mutation in STAT1, c.884C>A (exon 10), T295Y, not previously described. This new genetic mutation was validated using a STAT1 phosphorylation assay. Rosacae was related to Chronic demodocosis illustrated by important Demodex proliferation diagnosed via microscopic examination of cutaneous sample. A review of literature retrieved 20 other cases of STAT1 GOF mutation associated with rosacea, most of these cases had ocular involvement and an early onset. Conclusion: We describe a new STAT1 GOF mutation associated with a phenotype of CMC and rosacea. Rosacea related to chronic demodicosis appears as a novel and important symptom among some individuals with STAT1 GOF mutation.

Purpose: STAT1 mutations leading to a gain-of-function (GOF) are the first cause of Chronic Mucocutaneous Candidiasis (CMC). We describe a patient presenting a new GOF mutation in STAT1 with clinical symptoms consisting of CMC, recurrent pneumoniae and flowering rosacea with ocular involvement in relation to chronic demodicosis. Methods: A genetic analysis by targeted Next Generation Sequencing (DIPAI v.1) exploring the 98 genes most frequently involved in primary immunodeficiencies including STAT1 was performed to identify new mutations underlying STAT1 GOF. Results: NGS (DIPAI panel) identify a new missense mutation in STAT1, c.884C>A (exon 10), T295Y, not previously described. This new genetic mutation was validated using a STAT1 phosphorylation assay. Rosacae was related to Chronic demodocosis illustrated by important Demodex proliferation diagnosed via microscopic examination of cutaneous sample. A review of literature retrieved 20 other cases of STAT1 GOF mutation associated with rosacea, most of these cases had ocular involvement and an early onset. Conclusion: We describe a new STAT1 GOF mutation associated with a phenotype of CMC and rosacea. Rosacea related to chronic demodicosis appears as a novel and important symptom among some individuals with STAT1 GOF mutation.

Inborn errors of mucocutaneous immunity to Candida albicans in humans: a role for IL-17 cytokines?

Gain-of-function STAT1 mutations are associated with PD-L1 overexpression and a defect in B-cell survival

PULMONARY HYPERTENSION IN A CHILD WITH STAT3 GAIN OF FUNCTION MUTATION-ASSOCIATED INTERSITIAL LUNG DISEASE

PurposeHeterozygous missense STAT1 mutations leading to a gain of function (GOF) are the most frequent genetic cause of chronic mucocutaneous candidiasis (CMC). We describe the case of a patient presenting a new GOF mutation of STAT1 with the clinical symptoms of CMC, recurrent pneumonia, and persistent central erythema with papulopustules with ocular involvement related to rosacea-like demodicosis.MethodsGenetic analysis via targeted next-generation sequencing (NGS; NGS panel DIPAI v.1) exploring the 98 genes most frequently involved in primary immunodeficiencies, including STAT1, was performed to identify an underlying genetic defect.ResultsNGS identified a novel variant of STAT1, c.884C>A (exon 10), p.T295Y, not previously described. This variant was found to be gain of function using an in vitro luciferase reporter assay. Rosacea-like demodicosis was confirmed by substantial Demodex proliferation observed via the microscopic examination of a cutaneous sample. A review of literature retrieved 20 other cases of STAT1 GOF mutations associated with early-onset rosacea-like demodicosis, most with ocular involvement.ConclusionWe describe a new STAT1 GOF mutation associated with a phenotype of CMC and rosacea-like demodicosis. Rosacea-like demodicosis appears as a novel and important clinical phenotype among patients with STAT1 GOF mutation.

STAT1 is a cytoplasmic transcription factor associated with cell growth regulation, differentiation, proliferation, metabolism, and apoptosis. IFN-mediated JAK/STAT signaling pathway is involved in eliminating intracellular pathogens and viruses. However, pathogenic variants in STAT1 can result in impaired or increased function. Increased activity or function in STAT1 was described in 2011 and is characterized by excessive phosphorylation of the transcription factor. Carriers can develop autoimmune and inflammatory diseases and are susceptible to fungal, viral, and bacterial infections. The early and common manifestation is chronic mucocutaneous candidiasis. Here, we report a clinical case of a patient with increased STAT1 activity or gain of function, which started in the first year of his life. He is currently 27 years old and has presented bacillus Calmette-Guérin and Mycobacterium tuberculosis infection, chronic mucocutaneous candidiasis, tinea capitis, and facial and ocular rosacea. HIV infection was ruled out. Given the clinical manifestations, an inborn error of immunity was suspected, specifically STAT1 with gain of function. The diagnosis was corroborated by the sequencing of multiple genes associated with inborn errors of immunity. The pathogenic variant c.961A>G (p.Arg321Gly) in the STAT1 gene, previously reported as a gain of function mutation, was found in the patient. Finally, this case illustrates that mutations in immune-associated genes can contribute to producing severe and recurrent infections, even in adult patients. Chronic mucocutaneous candidiasis should raise suspicion of gain of function in STAT1.

Chronic Mucocutaneous Candidiasis Due to Gain-of-Function Mutation in STAT1

STAT1 mutations cause chronic mucocutaneous candidiasis (CMC), while STAT3 mutations cause hyper-IgE syndrome (HIES). CMC and HIES patients have T helper (Th) 17 defects suffering from mucosal Candida infections, but only patients with HIES show an allergic phenotype with eczema, eosinophilia and high IgE levels. We investigated whether differential Th2 and Th9 responses may explain the clinical differences. Peripheral blood mononuclear cells of patients with CMC (n = 4), patients with HIES (n = 4), patients with atopic dermatitis (n = 4) and healthy volunteers (n = 13) were stimulated with Candida and Staphylococcus aureus, with and without IL-4. The cytokines IL-5, IL-13, IL-9, IL-17 and TGFβ and regulatory T cells were measured in cell culture supernatants by ELISA or flow cytometry, respectively. Peripheral blood mononuclear cells of patients with CMC showed a significantly impaired production of the Th2 cytokines IL-5 and IL-13, especially in the presence of IL-4. Moreover, IL-9 production was significantly lower in patients with CMC compared to healthy controls. In contrast, patients with HIES and patients with AD showed normal IL-5 and IL-13 production, while IL-9 production was significantly lower in patients with HIES compared to healthy controls. Although TGFβ was involved in the IL-4-induced IL-9 production, TGFβ levels and the frequency of regulatory T cells did not differ between patients with HIES and controls. Flow cytometry analysis demonstrated an IL-9+ IL-17+ CD4+ subset in healthy controls after stimulation with Candida which was less present in patients with HIES. Patients with CMC have a general Th defect including Th2 and Th9, while patients with HIES have normal Th2 cytokines. These differences are in line with their clinical presentation. Surprisingly, the allergic cytokine IL-9 was deficient in both HIES and CMC, suggesting a Th-17-derived origin.

Heterozygous STAT1 gain-of-function (GOF) mutations result in a combined form of immunodeficiency which is the most common genetic cause of chronic mucocutaneous candidiasis (CMC). We present a pedigree with a GOF mutation in STAT1, manifesting with chronic demodicosis in the form of a facial papulopustular eruption, blepharitis, and chalazion. So far, demodicosis has been described in only one family with STAT1-GOF mutation. We suggest that chronic demodicosis is an under-recognized feature of the immune dysregulation disorder caused by STAT1 gain-of-function mutations.

Heterozygous STAT1 Gain-of-Function (GOF) mutations are the most common cause of chronic mucocutaneous candidiasis (CMC) among Inborn Errors of Immunity. Clinically, these mutations manifest as a broad spectrum of immune dysregulation, including autoimmune diseases, vascular disorders, and malignancies. The pathogenic mechanisms of immune dysregulation and its impact on immune cells are not yet fully understood. In treatment, JAK inhibitors have shown therapeutic effectiveness in some patients. We analyzed clinical presentations, cellular phenotypes, and functional impacts in five Taiwanese patients with STAT1 GOF. We identified two novel GOF mutations in 5 patients from 2 Taiwanese families, presenting with symptoms of CMC, late-onset rosacea, and autoimmunity. The enhanced phosphorylation and delayed dephosphorylation were displayed by the patients' cells. There are alterations in both innate and adaptive immune cells, including expansion of CD38+HLADR +CD8+ T cells, a skewed activated Tfh cells toward Th1, reduction of memory, marginal zone and anergic B cells, all main functional dendritic cell lineages, and a reduction in classical monocyte. Baricitinib showed therapeutic effectiveness without side effects. Our study provides the first comprehensive clinical and molecular characteristics in STAT1 GOF patient in Taiwan and highlights the dysregulated T and B cells subsets which may hinge the autoimmunity in STAT1 GOF patients. It also demonstrated the therapeutic safety and efficacy of baricitinib in pediatric patient. Further research is needed to delineate how the aberrant STAT1 signaling lead to the changes in cellular populations as well as to better link to the clinical manifestations of the disease.

ObjectiveGermline heterozygous gain-of-function (GOF) mutations in STAT1 impair IL-17-mediated immunity, resulting in carriers’ susceptibility to chronic mucocutaneous candidiasis (CMC). JAK inhibitors have shown therapeutic effectiveness in patients with STAT1-GOF mutations.MethodsThe mutation was detected using whole-exome sequencing (WES) and confirmed by Sanger sequencing. The functional impact of the mutation was verified by luciferase reporter assay. The phosphorylation level of STAT1 in patient cells, the phenotyping of leukocyte subtypes, and serum cytokine levels were determined by flow cytometry.ResultsThe patient with CMC harbors a heterozygous missense mutation in STAT1 (c.1078G > C, p.V360L). This mutation was functionally validated as a GOF mutation based on functional analysis of the variant and enhanced phosphorylation upon IFN-γ stimulation in the patient’s cells. Additionally, the patient demonstrated a decreased proportion of CD4 + T cells, NK cells, and Th17 cells. Flow cytometry analysis revealed a significant decrease in the expression of IL-17 A in CD4 + T cells from the patient. Serological test results showed that the patient’s IgM level was decreased, while the levels of IL-2, IL-5, IL-6 and TNF-α were elevated. Topical application of ruxolitinib demonstrated therapeutic efficacy.ConclusionsThe present study reports a pediatric patient with CMC who carries a novel GOF mutation in STAT1. This mutation may impair IL-17 immunity, which could potentially increase the patient’s susceptibility to CMC. However, further research is needed to elucidate the underlying mechanism. Although ruxolitinib shows potential as a therapeutic option for CMC, its clinical efficacy requires further validation through experimental studies and long-term patient follow-up.

There is a gap in clinical knowledge regarding associations between specific inborn errors of immunity (IEIs) and rheumatologic diseases. This study reports the frequency of rheumatologic conditions in a large cohort of patients with IEI using the USIDNET (United States Immunodeficiency Network) registry. We used the USIDNET registry to conduct the analysis. We included all IEI patients within the registry for whom a diagnosed rheumatologic disease was reported. The total number of patients with IEI in our query was 5058. Among those, 278 (5.49%) patients had a diagnosis of rheumatologic disease. This cohort included 172 (61.8%) female and 106 (38.2%) male patients. Rheumatologic complications were highest in the interferonopathies (66.6%), autoimmune lymphoproliferative syndrome (ALPS) (13.7%), and immunoglobulin G subclass deficiency (IgGSD) (11.11%). Additionally, disease patterns were noted to be different in various IEI disease groups. Inflammatory myopathies were the most common rheumatologic condition in patients with X-linked agammaglobulinemia (1.65%), Sjogren's syndrome was the most common rheumatologic disease reported in ALPS patients (6.85%), and systemic lupus erythematosus was the most common rheumatologic disease in patients with chronic mucocutaneous candidiasis (CMC) (7.41%). Rheumatoid arthritis (RA) report rate was highest in patients with IgGSD (3.70%), specific antibody deficiency (SAD) (3.66%), and ALPS (2.74%). This study reports that rheumatologic diseases are frequently observed in patients with IEI. The frequency of different rheumatologic conditions was variable based on the underlying diagnosis. Clinicians caring for patients with IEI should be vigilant to monitor for rheumatologic complications. Key Points • The rates of reported rheumatologic diseases in the USIDNET registry are different in individual IEIs. • Further studies are needed to guide clinicians for detecting rheumatologic conditions earlier in patients with IEI.

A normal level of interferon (IFN) responsiveness via the Stat1 transcription factor is critical to the host, since decreased Stat1 signaling causes immune compromise and increased signaling is associated with inflammatory and neoplastic disease. Here we report how this balance may be influenced by novel alterations in the efficiency of Stat1 signaling. To enable disulfide-dependent and spontaneous formation of active Stat1 homodimer (as was done previously for Stat3), we engineered Stat1-CC with double-cysteine substitutions in the Src homology 2 (SH2)-homodimerization domain (at Ala-656 and Asn-658). In this case, however, mutant and wild-type Stat1 exhibited no difference inspontaneousdimerization. Moreover, Stat1-CC still required ligand-dependent Tyr-701 phosphorylation for function and exhibited hyperresponsiveness to IFN-beta (that depends on Stat1/Stat2 heterodimerization) as well as IFN-gamma (that depends on Stat1/Stat1 homodimerization). Hyperresponsivenss of Stat1-CC was accompanied by increased capacities for Tyr-701 phosphorylation and DNA binding, but these features were also found in a similarly substituted serine mutant (Stat1-SS) that showed no hyperresponsiveness to IFN-gamma. This finding raised the possibility that SH2 domain mutations also influence downstream transcriptional efficiency. Indeed, each of these mutations also enhanced recruitment of the normally rate-limiting p300/CREB-binding Protein (CBP) coactivator to the transcriptional complex in proportion to the level of IFN-driven transactivation and gene expression. Additional modifications indicated that the mutant residues in the SH2 domain appeared to cooperate with Ser-727 in the C-terminal domain to regulate p300/CBP interaction with Stat1. The profile of IFN responsiveness translated into the same progressive increase in the level of viral clearance from Stat1- to Stat1-SS- to Stat1-CC-expressing cells. Thus, SH2 domain determinants may be modified to direct better Stat1 phosphorylation, DNA binding, and coactivator recruitment to fully improve IFN efficacy.