Pulmonary Histopathology Findings in Patients With STAT3 Gain of Function Syndrome

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.

Early-onset, fatal interstitial lung disease in STAT3 gain-of-function patients

Gain-of-function variants in STAT3 are known to cause severe, multifaceted autoimmunity. Here we report three individuals with de-novo STAT3 GOF alleles and early-onset, severe interstitial lung disease manifesting during the first 3 years of life. Imaging and histology revealed different forms of interstitial pneumonia alongside fibrotic and cystic tissue destruction. Definitive diagnosis was established by postmortem whole exome sequencing and functional validation of two new STAT3 variants. Such lung-predominant forms of STAT3 GOF disease expand the phenotypic spectrum of diseases associated with activating STAT3 variants and add to our understanding of this life-threatening inborn error of immunity.