The link between rheumatic disorders and inborn errors of immunity

Innovations in the care of childhood interstitial lung disease associated with connective tissue disease and immune-mediated disorders

Childhood interstitial lung disease (chILD) associated with connective tissue and immune mediated disorders is the second most common chILD diagnostic category. As knowledge of the molecular and genetic underpinnings of these rare disorders advances, the recognized clinical spectrum of associated pulmonary manifestations continues to expand. Pulmonary complications of these diseases, including ILD, confer increased risk for morbidity and mortality and contribute to increased complexity for providers tasked with managing the multiple organ systems that can be impacted in these systemic disorders. While pulmonologists play an important role in diagnosis and management of these conditions, thankfully they do not have to work alone. In collaboration with a multidisciplinary team of subspecialists, the pulmonary and other systemic manifestations of these conditions can be managed effectively together. The goal of this review is to familiarize the reader with the classic patterns of chILD and other pulmonary complications associated with primary immune-mediated disorders (monogenic inborn errors of immunity) and acquired systemic autoimmune and autoinflammatory diseases. In addition, this review will highlight current, emerging, and innovative therapeutic strategies and will underscore the important role of multidisciplinary management to improving outcomes for these patients.

The autoimmune rheumatological presentation of Common Variable Immunodeficiency Disorders with an overview of genetic testing

Primary immunodeficiency Disorders (PIDS) are rare, mostly monogenetic conditions which can present to a number of specialties. Although infections predominate in most PIDs, some individuals can manifest autoimmune or inflammatory sequelae as their initial clinical presentation. Identifying patients with PIDs can be challenging, as some can present later in life. This is often seen in patients with Common Variable Immunodeficiency Disorders (CVID), where symptoms can begin in the sixth or even seventh decades of life. Some patients with PIDs including CVID can initially present to rheumatologists with autoimmune musculoskeletal manifestations. It is imperative for these patients to be identified promptly as immunosuppression could lead to life-threatening opportunistic infections in these immunocompromised individuals. These risks could be mitigated by prior treatment with subcutaneous or intravenous (SCIG/IVIG) immunoglobulin replacement or prophylactic antibiotics. Importantly, many of these disorders have an underlying genetic defect. Individualized treatments may be available for the specific mutation, which may obviate or mitigate the need for hazardous broad-spectrum immunosuppression. Identification of the genetic defect has profound implications not only for the patient but also for affected family members, who may be at risk of symptomatic disease following an environmental trigger such as a viral infection. Finally, there may be clinical clues to the underlying PID, such as recurrent infections, the early presentation of severe or multiple autoimmune disorders, as well as a relevant family history. Early referral to a clinical immunologist will facilitate appropriate diagnostic evaluation and institution of treatment such as SCIG/IVIG immunoglobulin replacement. This review comprises three sections; an overview of PIDs, focusing on CVID, secondly genetic testing of PIDs and finally the clinical presentation of these disorders to rheumatologists.

Functional genomics in inborn errors of immunity

Inborn errors of immunity (IEI) comprise a diverse spectrum of 485 disorders as recognized by the International Union of Immunological Societies Committee on Inborn Error of Immunity in 2022. While IEI are monogenic by definition, they illuminate various pathways involved in the pathogenesis of polygenic immune dysregulation as in autoimmune or autoinflammatory syndromes, or in more common infectious diseases that may not have a significant genetic basis. Rapid improvement in genomic technologies has been the main driver of the accelerated rate of discovery of IEI and has led to the development of innovative treatment strategies. In this review, we will explore various facets of IEI, delving into the distinctions between PIDD and PIRD. We will examine how Mendelian inheritance patterns contribute to these disorders and discuss advancements in functional genomics that aid in characterizing new IEI. Additionally, we will explore how emerging genomic tools help to characterize new IEI as well as how they are paving the way for innovative treatment approaches for managing and potentially curing these complex immune conditions.

What can inherited immunodeficiencies reveal about pyoderma gangrenosum?

Pyoderma gangrenosum (PG) is a rare ulcerative neutrophilic dermatosis that is occasionally associated with primary immunodeficiency. Though contributions from dysregulation of the innate immune system, neutrophil dysfunction and genetic predisposition have been postulated, the precise pathogenesis of PG has not yet been elucidated. This article reviews reported cases of coexisting PG and primary immunodeficiency in order to gain insight into the complex pathophysiology of PG. Our findings suggest that variations in genes such as RAG1, ITGB2, IRF2BP2 and NFκB1 might play a role in genetically predisposing patients to develop PG. These studies support the feasibility of the role of somatic gene variation in the pathogenesis of PG which warrants further exploration to guide targeted therapeutics.

Rituximab to treat prolidase deficiency due to a novel pathogenic copy number variation in PEPD

Prolidase deficiency (PD) is a rare autosomal recessive inborn error of immunity caused by biallelic homozygous or compound heterozygous loss-of-function mutations in PEPD, the gene that encodes prolidase. PD typically manifests with variable dysmorphic features, chronic cutaneous ulcers, recurrent infections and autoimmune features, including systemic lupus erythematosus. So far, there is no consensus regarding treatment of PD and its autoimmune manifestations. Here, we present a 28-year-old female patient with PD due to a novel homozygous intragenic deletion in PEPD, diagnosed at the age of 6 years and 7 months with an undifferentiated connective tissue disease that, apart from its very early onset, would be consistent with the diagnosis of Sjögren's syndrome. Steroids and diverse conventional synthetic disease-modifying antirheumatic drugs failed to control PD-associated vasculitis and mucocutaneous ulcerations and led to infectious complications, including cytomegalovirus colitis. Introduction of rituximab (RTX) treatment in this patient led to sustained recession of mucocutaneous ulceration, enabling tapering of steroids. High interleukin-1β (IL-1β) production by this patient's monocytes, together with the detection of both IL-1β and interleukin-18 (IL-18) in her serum, suggest enhanced inflammasome activation in PD, whereas the therapeutic efficacy of RTX implies a role for CD20 positive B cells in the complex immunopathogenesis of PD.