Novel STAT-3 gain-of-function variant with hypogammaglobulinemia and recurrent infection phenotype

Infections in Disorders of Immune Regulation

Primary immune regulatory disorders (PIRDs) constitute a spectrum of inborn errors of immunity (IEIs) that are primarily characterized by autoimmunity, lymphoproliferation, atopy, and malignancy. In PIRDs, infections are infrequent compared to other IEIs. While susceptibility to infection primarily stems from antibody deficiency, it is sometimes associated with additional innate immune and T or NK cell defects. The use of immunotherapy and chemotherapy further complicates the immune landscape, increasing the risk of diverse infections. Recurrent sinopulmonary infections, particularly bacterial infections such as those associated with staphylococcal and streptococcal organisms, are the most reported infectious manifestations. Predisposition to viral infections, especially Epstein-Barr virus (EBV)-inducing lymphoproliferation and malignancy, is also seen. Notably, mycobacterial and invasive fungal infections are rarely documented in these disorders. Knowledge about the spectrum of infections in these disorders would prevent diagnostic delays and prevent organ damage. This review delves into the infection profile specific to autoimmune lymphoproliferative syndrome (ALPS), Tregopathies, and syndromes with autoimmunity within the broader context of PIRD. Despite the critical importance of understanding the infectious aspects of these disorders, there remains a scarcity of comprehensive reports on this subject.

Understanding the Spectrum of Immune Dysregulation Manifestations in Autoimmune Lymphoproliferative Syndrome and Autoimmune Lymphoproliferative Syndrome-like Disorders

As a disorder of immune dysregulation, autoimmune lymphoproliferative syndrome (ALPS) stems from pathogenic variants in the first apoptosis signal-mediated apoptosis (Fas) and Fas-ligand pathway that result in elevations of CD3+ TCRαβ+ CD4- CD8- T cells along with chronic lymphoproliferation, a heightened risk for malignancy, and importantly for the rheumatologist, increased risk of autoimmunity. While immune cytopenias are the most encountered autoimmune phenomena, there is increasing appreciation for ocular, musculoskeletal, pulmonary and renal inflammatory manifestations similar to more common rheumatology diseases. Additionally, ALPS-like conditions that share similar clinical features and opportunities for targeted therapy are increasingly recognized via genetic testing, highlighting the need for rheumatologists to be facile in the recognition and diagnosis of this spectrum of disorders. This review will focus on clinical and laboratory features of both ALPS and ALPS-like disorders with the intent to provide a framework for rheumatologists to understand the pathophysiologic drivers and discriminate between diagnoses.

A Novel STAT3 Gain-of-Function Mutation in Fatal Infancy-Onset Interstitial Lung Disease

Signal transducer and activator of transcription 3 (STAT3) gain-of-function (GOF) mutations cause early-onset immune dysregulation syndrome, characterized by multi-organ autoimmunity and lymphoproliferation. Of them, interstitial lung disease (ILD) usually develops after the involvement of other organs, and the onset time is childhood and beyond rather than infancy. Here, we reported a patient who presented with fatal infancy-onset ILD, finally succumbing to death. Next-generation sequencing identified a novel heterozygous mutation in STAT3 (c.989C>G, p.P330R). Functional experiments revealed it was a gain-of-function mutation. Upon interleukin 6 stimulation, this mutation caused a much higher activation of STAT3 than the wild-type control. In addition, the mutation also activated STAT3 under the steady state. The T helper 17 cell level in the patient was significantly higher than that in normal controls, which may contribute to the autoimmune pathology caused by the STAT3P330R mutation. Apart from Janus kinase (JAK) inhibitors, we also provided experimental evidence of a STAT3 selective inhibitor (Stattic) effectively suppressing the activation of mutant STAT3 in vitro. Collectively, our study expanded the clinical spectrum of STAT3 GOF syndrome. STAT3 GOF mutation appears as a new etiology of ILD and should be considered in patients with early-onset ILDs. In addition to JAK inhibitors, the specific STAT3 inhibitor would be an appealing option for the targeted treatment.

STAT3 gain-of-function syndrome

STAT3 gain-of-function (GOF) syndrome is a multi-organ primary immune regulatory disorder characterized by early onset autoimmunity. Patients present early in life, most commonly with lymphoproliferation, autoimmune cytopenias, and growth delay. However, disease is often progressive and can encompass a wide range of clinical manifestations such as: enteropathy, skin disease, pulmonary disease, endocrinopathy, arthritis, autoimmune hepatitis, and rarely neurologic disease, vasculopathy, and malignancy. Treatment of the autoimmune and immune dysregulatory features of STAT3-GOF patients relies heavily on immunosuppression and is often challenging and fraught with complications including severe infections. Defects in the T cell compartment leading to effector T cell accumulation and decreased T regulatory cells may contribute to autoimmunity. While T cell exhaustion and apoptosis defects likely contribute to the lymphoproliferative phenotype, no conclusive correlations are yet established. Here we review the known mechanistic and clinical characteristics of this heterogenous PIRD.

Novel STAT-3 gain-of-function variant with hypogammaglobulinemia and recurrent infection phenotype

Signal transducer and activator of transcription 3 (STAT‐3) gain‐of‐function (GOF) syndrome is an early‐onset monogenic inborn error of immunity characterized by multi‐organ autoimmune disorders, growth failure and lymphoproliferation. We describe that STAT‐3 GOF syndrome may be presented with hypogammaglobulinemia and recurrent severe upper and lower respiratory tract infections. In addition, the patient had lymphoproliferation, short stature and interstitial lung disease. Chest computerized tomography examinations showed mild bronchiectasis with areas of non‐fibrosing alveolar‐interstitial disease and maldevelopment of bilateral first ribs. Using Sanger sequencing, we revealed a novel c.508G>C, p.D170H STAT‐3 variant affecting the coiled coil domain of STAT‐3. Functional studies confirmed that p.D170H was a GOF variant, as shown by increased phosphorylated STAT‐3 (pSTAT‐3) and STAT‐3 transcriptional activity. Our observation suggests that STAT‐3 GOF syndrome can manifest in early childhood with hypogammaglobulinemia and recurrent severe respiratory tract infections. We suggest that patients with lymphoproliferation, hypogammaglobulinemia and severe recurrent infections should be screened for STAT‐3 variants, even if autoimmune manifestations are missing.