Cytokines and soluble receptors of the interleukin-1 family in Schnitzler syndrome

Malignant Evolution of Schnitzler Syndrome to Waldenström Macroglobulinemia: a Case Report

Introduction: Schnitzler syndrome (SchS), first described in 1972, is a rare autoinflammatory condition characterized by chronic urticaria and monoclonal gammopathy of IgM or, exceptionally, IgG profile. Additional features include recurrent fever, evidence of abnormal bone remodeling, a neutrophilic dermal infiltrate on skin biopsy, leukocytosis or elevated C-reactive protein, according to the Strasbourg criteria.

Case Presentation: We describe the case of a 56-year-old Caucasian male patient, who suffered from chronic urticaria, moderate-grade fever, severe generalized fatigue and arthralgias. After five years of chronic disease evolution, he was referred to the hematology department where he was found to have IgM kappa light chain monoclonal gammopathy. The constellation of symptoms, a negative rheumatologic workup, and the finding of IgM monoclonal gammopathy determined the diagnosis of Schnitzler syndrome. Bone marrow biopsy proved the association of Waldenström macroglobulinemia.

Conclusion: The main goal of our case report was to highlight the clinical features and treatment, with emphasis on the hematological aspects, to provide a better understanding and to raise awareness of Schnitzler syndrome among healthcare professionals.

What Is IL-1 for? The Functions of Interleukin-1 Across Evolution

Interleukin-1 is a cytokine with potent inflammatory and immune-amplifying effects, mainly produced by macrophages during defensive reactions. In mammals, IL-1 is a superfamily of eleven structurally similar proteins, all involved in inflammation or its control, which mainly act through binding to specific receptors on the plasma membrane of target cells. IL-1 receptors are also a family of ten structurally similar transmembrane proteins that assemble in heterocomplexes. In addition to their innate immune/inflammatory effects, the physiological role of IL-1 family cytokines seems to be linked to the development of adaptive immunity in vertebrates. We will discuss why IL-1 developed in vertebrates and what is its physiological role, as a basis for understanding when and how it can be involved in the initiation and establishment of pathologies.

Schnitzler syndrome and Schnitzler-like syndromes

Schnitzler syndrome is a rare disease of adult-onset with main features including chronic urticarial rash, recurrent fever, arthralgia or arthritis, monoclonal gammopathy of undetermined significance (MGUS), and marked systemic inflammation. Schnitzler syndrome is often underdiagnosed. Patients with Schnitzler syndrome may present to dermatologists and allergists for urticaria, hematologists for MGUS, or rheumatologists for arthritis. It is important to recognize Schnitzler syndrome for its remarkable response to interleukin (IL)-1 blockade. Besides, many cases of Schnitzler-like syndromes do not meet the diagnostic criteria of classical Schnitzler syndrome but display excellent response to IL-1 inhibitors. The overly produced IL-1 is the result of a somatic mosaic gain of function mutation of NLRP3 (nucleotide-binding oligomerization domain [NOD]-like receptor [NLR] family pyrin domain containing 3) gene in some patients with Schnitzler-like syndromes. Inflammasome activation is evident in patients with classical Schnitzler syndrome although no NLRP3 gene mutation is identified. Collectively, Schnitzler syndrome and Schnitzler-like syndromes represent a spectrum of IL-1 mediated adult-onset autoinflammatory diseases.

Therapeutic potential of targeting IL-1 family cytokines in chronic inflammatory skin diseases

The interleukin-1 (IL-1) family of cytokines is a central regulator of a myriad of immunological responses. It comprises several cytokines, including those belonging to the IL-1, IL-36 and IL-18 subfamilies, as well as IL-33. The IL-1 family primarily plays a role in orchestrating innate immune responses but also in adaptive immunity. Increased interest in the IL-1 family occurred following the discovery that dysregulation of IL-1 signalling underlies the pathogenesis of several monogenic auto-inflammatory diseases, characterized by sterile inflammation involving the skin and other organs. This also provided increased understanding of the role of innate immunity and the IL-1 family in polygenic auto-inflammatory skin conditions, such as neutrophilic dermatoses, as well as in some of the most common chronic inflammatory skin diseases, such as psoriasis or hidradenitis suppurativa. Several therapeutic agents have been developed to inhibit the IL-1 family members and their signalling pathways. These have shown therapeutic efficacy in several chronic inflammatory skin disorders. The aim of this review is to thoroughly describe the consequences of pathological dysregulation of IL-1, IL-33, IL-36, IL-18 pathways in dermatological conditions and to provide a forward-looking update on therapeutic strategies targeting signalling by IL-1 family cytokines.

The revisited role of interleukin-1 alpha and beta in autoimmune and inflammatory disorders and in comorbidities

The interleukin (IL) 1 family of cytokines is noteworthy to have pleiotropic functions in inflammation and acquired immunity. Over the last decades, several progresses have been made in understanding the function and regulation of the prototypical inflammatory cytokine (IL-1) in human diseases. IL-1α and IL-1β deregulated signaling causes devastating diseases manifested by severe acute or chronic inflammation. In this review, we examine and compare the key aspects of IL-1α and IL-1β biology and regulation and discuss their importance in the initiation and maintenance of inflammation that underlie the pathology of many human diseases. We also report the current and ongoing inhibitors of IL-1 signaling, targeting IL-1α, IL-1β, their receptor or other molecular compounds as effective strategies to prevent or treat the onset and progression of various inflammatory disorders.

Schnitzler Syndrome in a 27-Year-Old Man: Diagnostic and Therapeutic Dilemma in Adult Auto-Inflammatory Syndromes A Case Report and Literature Review

A 32-year-old-man, with a history of chronic urticaria from the age of 27, diagnosed with an adult-onset Still’s disease and received a low dose of glucocorticoids, methotrexate and tocilizumab. Despite the long-term combined treatments, he suffered from chronic urticaria, low-grade fever and bone pain. He was found to have high inflammatory markers, hypogammaglobulinemia, monoclonal IgM – kappa light chain in serum and increased radiotracer uptake in the whole bone scintigraphy. No pathological variants for monogenic autoinflammatory diseases were present in the genome exome sequencing. These investigations confirmed the diagnosis of Schnitzler syndrome, which is an exception before the age of 35. Switching from tocilizumab to interleukin 1 receptor inhibitor, anakinra led to a full clinical response and normalisation of inflammatory markers. Patients with a history of fever and chronic urticaria are routinely tested for monoclonal gammopathy in the context of malignancy, but it should also be considered as a sign of the autoinflammatory syndrome. The Schnitzler syndrome and the adult-onset Still’s disease share common features, so the diagnosis requires a thorough investigation to establish an optimal treatment. In the diagnostic algorithm, monoclonal gammopathy is usually considered red flag for malignancy but might be overlooked as a criterion of Schnitzler syndrome, particularly in young adults. We confirm that the interleukin 1 inhibitor should be the first line of therapy in Schnitzler syndrome, and in the presented case we found it more effective than the interleukin 6 blockade. The main goal of this paper is to increase awareness of Schnitzler syndrome among health care professionals. We aim to present features which can be helpful in differential diagnosis.

The IL-1 family cytokines and receptors in autoimmune diseases

The role of the cytokines and receptors of the IL-1 family in inflammation is well known. Several cytokines of the family have a powerful inflammatory activity, with IL-1β being the best-characterized factor. The inflammatory activity of IL-1 cytokines is regulated by other factors of the family, including receptor antagonists, soluble receptors and anti-inflammatory cytokines. The causative role of IL-1β is well-established in autoinflammatory diseases, mainly due to gain-of-function mutations in genes encoding the IL-1β-maturing inflammasome. Exaggerated production of IL-1β and IL-18 correlates with disease and disease severity also in several autoimmune and chronic inflammatory and degenerative pathologies, although it is not clear whether they have a causative role or are only involved in the downstream disease symptoms. A better understanding of the pathological role of IL-1 family cytokines in autoimmunity involves a deeper evaluation, in the pathological situations, of the possible anomalies in the feed-back anti-inflammatory mechanisms that in physiological reactions control and dump IL-1-mediated inflammation. Thus, we expect that IL-1 cytokines may be pathogenic only when, in addition to enhanced production, there is a concomitant failure of their control mechanisms. In this review we will examine the current knowledge on the role of IL-1 family cytokines in autoimmune and chronic inflammatory and degenerative diseases, with a particular focus on their endogenous control mechanisms, mainly based on soluble receptors/inhibitors and receptor antagonists. This will allow us to formulate a knowledge-based hypothesis on the involvement of IL-1 cytokines in the pathogenesis vs. the clinical features of these diseases.

The innate immune perspective of autoimmune and autoinflammatory conditions

Innate immunity is one of two immune defence system arms. It is present at birth and does not require ‘learning’ through exposure to foreign organisms. It activates various mechanisms collectively to eliminate pathogens and hold an infection until the adaptive response are mounted. The innate immune system consists of four elements: the epithelial barrier, cells (e.g. macrophages, NK cells), plasma proteins (e.g. complement) and cytokines. These components act in concert to induce complex processes, as well as recruitment, activation and differentiation of adaptive responses. The innate response is more than just the ‘first line of defence’, as it essentially withholds the vast majority of any intruder, has a complex interplay with the adaptive arm and is crucial for survival of the host. Finally, yet importantly, a myriad of diseases has been linked with innate immune dysregulation. In this mini-review we will shed some light on these conditions, particularly regarding autoinflammatory ones.