Schnitzler syndrome: beyond the case reports: review and follow-up of 94 patients with an emphasis on prognosis and treatment

Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort

The objectives of the study were to present the experience of diagnosis, management, and therapy with IL-1 inhibitors in patients with Schnitzler's syndrome (SchS) according to a multicenter Russian cohort. An observational retrospective study for a 10-year period (2012-2022) involved 17 patients with SchS who were admitted to the hospital or were observed on an outpatient basis (eight women and nine men). The diagnosis of all of them corresponded to the Strasbourg diagnostic criteria. The age of patients ranged from 25 to 81 years (Me 53[46; 56]). The age at the time of the onset of the disease ranged from 20 to 72 years (Me 46[39; 54]), the duration of the disease before diagnosis ranged from 1 to 35 years (Me 6.5[3; 6]), in three patients it exceeded 10 years, in the rest it ranged from 1 to 8 years. Infectious and lymphoproliferative diseases, monogenic AIDs (CAPS, TRAPS, and HIDS) were excluded from all patients at the prehospital stage. The referral diagnosis for all of them was Still 's disease in adults. Clinical manifestations of the disease in all patients included fatigue, lethargy, fatigue, rash, and fever. In all patients, skin elements were urticular and were accompanied by itching in 6 (37.5%) patients. Bone pain was observed in 12 (70.6%) patients; arthralgias, in 16 (94.1%); arthritis, in 9 (52.9%); myalgia, in 7 (41.2%); and weight loss, in 4 (23.5%). Lymphadenopathy was detected in 6 (35.3%) patients; enlarged liver, in 6 (35.3%); pericarditis, in 4 (23.5%); angioedema, in 6 (35.3); redness and dryness in the eyes, in 3 (17.6%); sore throat, in 2 (11.8%); abdominal pain, in 1 (5.9%), distal polyneuropathy, in 2 (11.8%); paraesthesia, in 1 (5.9%); and chondritis of the auricles, in 1 (5.9%). Monoclonal gammopathy was detected in all patients with a secretion level of 2.9-15.1 g/L: IgMk (n = 10, 64.7%), less often IgMλ (n = 2), IgGk (n = 2), IgGλ (n = 1), and IgAλ (n = 1). Ben-Jones protein was not detected in any of them. All patients had an increased level of ESR and CRP. Before inclusion in the study, 16 patients received GCs (94.1%) with a temporary effect that disappeared with dose reduction or cancellation. Seven patients received cDMARDs, including methotrexate (5), hydroxychloroquine (2), and cyclophosphamide (1). All patients received NSAIDs and antihistamines, as well as biologics, including the anti-B-cell drug rituximab (1), monoclonal ABs to IgE omalizumab (2, 1 without effect and 1 with partial effect), IL-1i canakinumab (n = 10, 58.8%) subcutaneously once every 8 weeks, and anakinra (n = 4, 23.5%) subcutaneously daily. The duration of taking anakinra, which was prescribed in the test mode, ranged from 1 week to 2.5 months with a further switch to canakinumab in 3 patients. The duration of taking canakinumab at the time of analysis ranged from 7 months to 8 years. Against the background of treatment with IL-1i, 10 out of 11 (90.9%) patients received a complete response in terms of the clinical manifestations of the disease and a decrease in the level of ESR and CRP within a few days. In one patient, a partial response to the administration of anakinra was detected; however, after switching to canakinumab, the effect of treatment was finally lost. One patient received IL-6i for 8 months with an incomplete effect and a positive dynamics after switching to anakinra. Thus, anakinra was initially prescribed to four patients and changed to canakinumab in two of them; canakinumab was started as the first drug in seven patients. Treatment with anakinra was continued in two patients; with canakinumab, in nine patients. In one patient, due to the persistent absence of relapses, the interval between canakinumab injections was increased to 5 months without signs of reactivation; however, subsequently, against the background of stress and relapses of the disease, the intervals were reduced to 4 months. A healthy child was born by the same patient on the background of treatment. The tolerability of therapy was satisfactory in all patients, no SAEs were noted. SchS is a rare multifactorial/non-monogenic AID that should be differentiated from a number of rheumatic diseases and other AIDs. The onset in adulthood, the presence of recurrent urticarial rashes in combination with fever and other manifestations of a systemic inflammatory response are indications for examination for monoclonal secretion. The use of short- or long-acting IL-1i is a highly effective and safe option in the treatment of such patients.

[Autoinflammatory syndromes]

The concept of autoinflammation includes a heterogeneous group of monogenic and polygenic diseases. These are characterized by excessive activation of the innate immune system without antigen-specific T cells or autoantibodies. The diseases are characterized by periodic episodes of fever and increased inflammation parameters. Monogenic diseases include familial Mediterranean fever (FMF) and the newly described VEXAS (vacuoles, E1 enzyme, X‑linked, autoinflammatory, somatic) syndrome. Heterogeneous diseases include adult-onset Still's disease and Schnitzler syndrome. Treatment is aimed at preventing the excessive inflammatory reaction in order to avoid long-term damage, such as amyloid A (AA) amyloidosis.

Proposal of a new clinical entity: Paraprotein negative IL-1 mediated inflammatory dermatosis (PANID) that may precede Schnitzler syndrome

Schnitzler syndrome (SchS) is an autoinflammatory disease that is defined by the presence of 2 obligate criteria; an IgM or IgG monoclonal paraprotein and a chronic urticarial rash. Typically, there is an excellent clinical response to IL-1 antagonism. There are reports in the literature of a variant type of SchS that does not fulfil the 2 obligate criteria but responds to IL-1 blockade. Equally, there are reports of an urticarial rash preceding the development of a paraprotein by several years. We describe 3 cases in this manuscript. The first fits the Strasbourg diagnostic criteria of SchS, Simon and Asli (2013); however, with several decades of diagnostic delay. The second case at initial presentation did not fit the major criteria for SchS; however, later developed a monoclonal IgM. Finally we report, a third case that has not yet been confirmed to have a monoclonal IgM/IgG at the time of writing despite 12 years of symptoms and in whom a somatic autoinflammatory disorder remains within the differential. All cases responded strikingly to anakinra, an IL-1 receptor blocker. We propose a new clinical entity, paraprotein negative IL-1 mediated inflammatory dermatosis (PANID), that may act as a precursor or risk factor for the development of SchS or other autoinflammatory conditions.

Chronic Urticaria and Angioedema: Masqueraders and Misdiagnoses

Chronic urticaria is a common condition presenting with intensely pruritic wheals. Although individual lesions resolve within 24 hours, by definition, chronic urticaria lasts for a duration of at least 6 weeks. Both spontaneous and inducible forms exist. In the spontaneous variant, chronic urticaria occurs in the absence of clearly identifiable triggers. In chronic inducible urticaria, specific triggers may include dermatographism, cholinergic (heat), cold, exercise, delayed pressure, and solar. Extensive laboratory evaluation for chronic spontaneous urticaria is not required unless indicated by clinical history or physical examination. Angioedema describes sudden onset of localized edema involving the deep layers of the skin and submucosal tissues. It can be seen in isolation or in conjunction with chronic urticaria. Angioedema typically resolves slower than wheals, taking up to 72 hours or longer. Histamine- and bradykinin-mediated forms exist. Both chronic urticaria and angioedema have many mimics, and a broad range of differential diagnoses should be considered. Importantly, an incorrect diagnosis may have significant implications for the additional investigation, treatment, and prognosis of the affected patient. The aim of this article is to discuss the characteristics of chronic urticaria and angioedema, and an approach to the investigation and diagnosis of their mimics.

Therapy resistant urticaria as a long-term symptom of an incomplete Schnitzler syndrome

BACKGROUND

Recurring therapy resistant hives, accompanied by IgM-gammopathy, fever and joint pain can indicate Schnitzler syndrome, a rare autoimmune disorder. There is currently no approved treatment, but complete remission of symptoms can be induced with IL-1 antagonists.

CASE PRESENTATION

A patient with a history of chronic urticaria presented frequently at the outpatient clinic with severe hives and was treated unsuccessfully with antihistamines and omalizumab. After several years, additional symptoms such as joint pain, recurrent fever, and IgM-gammopathy developed. After the diagnostic criteria for Schnitzler syndrome were met, treatment with anakinra was initiated and resulted in an improvement of the symptoms. Shortly after the first injection, the patient developed large and painful erythematous lesions at the injection sites, leading to discontinuation of treatment and a rapid recurrence of symptoms. Subsequently, treatment with a longer-acting IL-1 antagonist (canakinumab) was initiated, resulting in a complete remission of symptoms.

CONCLUSION

This case report demonstrates that patients with urticarial symptoms that are not relieved by typical treatments should prompt repeated reassessments of the diagnosis, even years later, because gammopathy and other diagnostic criteria for Schnitzler syndrome can occur with a delay.

[Autoinflammatory syndromes]

The concept of autoinflammation includes a heterogeneous group of monogenic and polygenic diseases. These are characterized by excessive activation of the innate immune system without antigen-specific T cells or autoantibodies. The diseases are characterized by periodic episodes of fever and increased inflammation parameters. Monogenic diseases include familial Mediterranean fever (FMF) and the newly described VEXAS (vacuoles, E1 enzyme, X‑linked, autoinflammatory, somatic) syndrome. Heterogeneous diseases include adult-onset Still's disease and Schnitzler syndrome. Treatment is aimed at preventing the excessive inflammatory reaction in order to avoid long-term damage, such as amyloid A (AA) amyloidosis.

Similarities and differences in autoinflammatory diseases with urticarial rash, cryopyrin-associated periodic syndrome and Schnitzler syndrome

Cryopyrin-associated periodic syndromes (CAPS) and Schnitzler syndrome (SchS) are autoinflammatory diseases that present with urticaria-like rashes. CAPS is characterized by periodic or persistent systemic inflammation caused by the dysfunction of the NLRP3 gene. With the advent of IL-1-targeted therapies, the prognosis of CAPS has improved remarkably. SchS is considered an acquired form of autoinflammatory syndrome. Patients with SchS are adults of relatively older age. The pathogenesis of SchS remains unknown and is not associated with the NLRP3 gene. Previously, the p.L265P mutation in the MYD88 gene, which is frequently detected in Waldenström macroglobulinemia (WM) with IgM gammopathy, was identified in several cases of SchS. However, because persistent fever and fatigue are symptoms of WM that require therapeutic intervention, it is a challenge to determine whether these patients truly had SchS or whether advanced WM was misidentified as SchS. There are no established treatments for SchS. The treatment algorithm proposed with the diagnostic criteria is to use colchicine as first-line treatment, and systemic administration of steroids is not recommended due to concerns about side effects. In difficult-to-treat cases, treatment targeting IL-1 is recommended. If targeted IL-1 treatment does not improve symptoms, the diagnosis should be reconsidered. We hope that the efficacy of IL-1 therapy in clinical practice will serve as a stepping stone to elucidate the pathogenesis of SchS, focusing on its similarities and differences from CAPS.

Dermatologic Manifestations of Noninflammasome-Mediated Autoinflammatory Diseases

Autoinflammatory diseases (AIDs) arise from disturbances that alter interactions of immune cells and tissues. They give rise to prominent (auto)inflammation in the absence of aberrant autoantibodies and/or autoreactive T cells. AIDs that are predominantly caused by changes in the inflammasome pathways, such as the NLRP3- or pyrin-associated inflammasome, have gained substantial attention over the last years. However, AIDs resulting primarily from other changes in the defense system of the innate immune system are less well-studied. These noninflammasome-mediated AIDs relate to, for example, disturbance in the TNF or IFN signaling pathways or aberrations in genes affecting the IL-1RA. The spectrum of clinical signs and symptoms of these conditions is vast. Thus, recognizing early cutaneous signs constitutes an important step in differential diagnoses for dermatologists and other physicians. This review provides an overview of the pathogenesis, clinical presentation, and available treatment options highlighting dermatologic aspects of noninflammasome-mediated AIDs.

Clinical Presentation of Schnitzler's Syndrome: A Rare Autoimmune Disease

Schnitzler's Syndrome (SS) is a rare late-onset acquired autoinflammatory disorder which consists of chronic urticaria associated with a monoclonal IgM-kappa gammopathy, arthralgias, skeletal hyperostosis, lymphadenopathy, and recurrent constitutional symptoms. The average age of diagnosis is 51 years with a slight male predominance with a male to female ratio of 1.6. Diagnosis of SS requires the presence of 2 major criteria including chronic urticaria and monoclonal IgM along with at least two of the following minor criteria: recurrent intermittent fevers, bone pain, arthralgias, elevated erythrocyte sedimentation rate (ESR), neutrophilic dermal infiltrate on skin biopsy, and leukocytosis or elevated C-reactive protein (CRP). Early diagnosis and clinical awareness are paramount in SS as it is associated with a 15-20% risk of lymphoproliferative malignancy. The median overall survival is 12.8 years. We present a case of a 39-year-old female with new onset urticaria associated with recurrent fevers and joint pain. Symptoms were refractory to steroids, and high dose antihistamines. Multi-disciplinary evaluation resulted in the ultimate diagnosis of Schnitzler's Syndrome. The patient was ultimately treated with canakinumab (Il-1 inhibitor), with near resolution of symptoms. This case demonstrates the importance of a broad differential diagnosis and maintaining a high clinical suspicion for rare diseases when presented with a complex form of an otherwise common condition.

Monoclonal gammopathies of clinical significance (MGCS): In pursuit of optimal treatment

Monoclonal gammopathy of clinical significance (MGCS) represents a new clinical entity referring to a myriad of pathological conditions associated with the monoclonal gammopathy of undetermined significance (MGUS). The establishment of MGCS expands our current understanding of the pathophysiology of a range of diseases, in which the M protein is often found. Aside from the kidney, the three main organ systems most affected by monoclonal gammopathy include the peripheral nervous system, skin, and eye. The optimal management of these MGUS-related conditions is not known yet due to the paucity of clinical data, the rarity of some syndromes, and limited awareness among healthcare professionals. Currently, two main treatment approaches exist. The first one resembles the now-established therapeutic strategy for monoclonal gammopathy of renal significance (MGRS), in which chemotherapy with anti-myeloma agents is used to target clonal lesion that is thought to be the culprit of the complex clinical presentation. The second approach includes various systemic immunomodulatory or immunosuppressive options, including intravenous immunoglobulins, corticosteroids, or biological agents. Although some conditions of the MGCS spectrum can be effectively managed with therapies aiming at the etiology or pathogenesis of the disease, evidence regarding other pathologies is severely limited to individual patient data from case reports or series. Future research should pursue filling the gap in knowledge and finding the optimal treatment for this novel clinical category.

New insights on multigenic autoinflammatory diseases

Autoinflammatory diseases are disorders of the innate immune system, which can be either monogenic due to a specific genetic mutation or complex multigenic due to the involvement of multiple genes. The aim of this review is to explore and summarize the recent advances in pathogenesis, diagnosis, and management of genetically complex autoinflammatory diseases, such as Schnitzler's syndrome; adult-onset Still's disease; synovitis, acne, pustulosis, hyperostosis, osteitis syndrome/chronic recurrent multifocal osteomyelitis/chronic non-bacterial osteomyelitis; Adamantiades-Behçet's disease; Yao syndrome; and periodic fever with aphthous stomatitis, pharyngitis, and adenitis syndrome. The PubMed database was screened for relevant articles using free text words and specific search strings. The search was limited to English-language articles, reporting the results of studies in humans, published through March 2021. Evidence from literature suggest that these rare multigenic autoinflammatory diseases can present with different clinical features and the diagnosis of these diseases can be challenging due to a combination of nonspecific manifestations that can be seen in a variety of other conditions. Diagnostic delays and disease complications may occur due to low disease awareness and the lack of pathognomonic markers. The pathogeneses of these diseases are complex and in some cases precise pathogenesis is not clearly understood. Conventional treatments are commonly used for the management of these conditions, but biologics have shown promising results. Biologics targeting proinflammatory cytokines including IL-1, IL-6, TNF-α, IL-17A and IL-18 have been shown to ameliorate signs and symptoms of different multigenic autoinflammatory diseases.

Unmet Medical Needs in Chronic, Non-communicable Inflammatory Skin Diseases

An estimated 20-25% of the population is affected by chronic, non-communicable inflammatory skin diseases. Chronic skin inflammation has many causes. Among the most frequent chronic inflammatory skin diseases are atopic dermatitis, psoriasis, urticaria, lichen planus, and hidradenitis suppurativa, driven by a complex interplay of genetics and environmental factors. Autoimmunity is another important cause of chronic skin inflammation. The autoimmune response may be mainly T cell driven, such as in alopecia areata or vitiligo, or B cell driven in chronic spontaneous urticaria, pemphigus and pemphigoid diseases. Rare causes of chronic skin inflammation are autoinflammatory diseases, or rheumatic diseases, such as cutaneous lupus erythematosus or dermatomyositis. Whilst we have seen a significant improvement in diagnosis and treatment, several challenges remain. Especially for rarer causes of chronic skin inflammation, early diagnosis is often missed because of low awareness and lack of diagnostics. Systemic immunosuppression is the treatment of choice for almost all of these diseases. Adverse events due to immunosuppression, insufficient therapeutic responses and relapses remain a challenge. For atopic dermatitis and psoriasis, a broad spectrum of innovative treatments has been developed. However, treatment responses cannot be predicted so far. Hence, development of (bio)markers allowing selection of specific medications for individual patients is needed. Given the encouraging developments during the past years, we envision that many of these challenges in the diagnosis and treatment of chronic inflammatory skin diseases will be thoroughly addressed in the future.

Case Report: Therapeutic Use of Ibrutinib in a Patient With Schnitzler Syndrome

Schnitzler syndrome is a rare adult-onset acquired autoinflammatory disorder typically characterized by chronic urticarial rash and immunoglobulin M (IgM) (rarely IgG) monoclonal gammopathy. Its clinical symptoms usually respond well to interleukin-1 blockade therapy, which, however, does not impact the underlying monoclonal gammopathy. Herein, we described a female patient who presented with urticarial rash, recurrent fevers, and fatigue for 7 years. Laboratory investigations revealed IgMκ monoclonal protein and MYD88 L265P mutation, but no lymphoplasmacytic lymphoma on bone marrow examination. She fulfilled the diagnosis of Schnitzler syndrome and was treated with the Bruton tyrosine kinase inhibitor ibrutinib in combination with prednisone. Her symptoms improved dramatically, and the level of IgMκ monoclonal protein also declined. She tolerated the treatment well. This case highlights the potential therapeutic role of Bruton tyrosine kinase inhibitors in Schnitzler syndrome.

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.

Refractory serum immunoglobulin M elevation during anti-interleukin (IL)-1- or IL-6-targeted treatment in four patients with Schnitzler syndrome

Schnitzler syndrome is characterized by chronic urticarial rash, neutrophilic dermal infiltrate, recurrent fever, bone pain, elevated C-reactive protein, and neutrophilic leukocytosis. The pathophysiology of Schnitzler syndrome is unknown, but it is considered to be an acquired form of an autoinflammatory disease because of the resemblance to clinical phenotypes of cryopyrin-associated periodic syndrome, in which a gain-of-function mutation in NLRP3 causes overexpression of interleukin (IL)-1β. Schnitzler syndrome is generally accompanied by a monoclonal immunoglobulin (Ig)M gammopathy with a long-term risk of lymphoproliferation that is possibly associated with an MYD88 mutation. Herein, we present the following four patients with Schnitzler syndrome: a 63-year-old woman; a 65-year-old man; a 43-year-old woman; and a 63-year-old woman. Each patient fulfilled the Strasbourg diagnostic criteria, but none of the patients had any mutation in NLRP3 or MYD88 detected in their peripheral blood. Although approved treatment options for Schnitzler syndrome are lacking, our patients were treated with IL-1-targeted therapy (anakinra or canakinumab) or anti-IL-6 (tocilizumab). The acute inflammatory clinical manifestations improved completely with canakinumab and partially with anakinra and tocilizumab, but the serum IgM levels were gradually increased in all patients, even during treatment. To determine whether treatment with anti-IL-1β or IL-6 prevents conversion to a hematopoietic disorder, further collection of cases and long-term follow-up will be needed.

Schnitzler's Syndrome: A Diagnostic Consideration in Evaluating the Constellation of Monoclonal Gammopathy and Chronic Urticaria

Schnitzler’s syndrome is a rare clinical entity characterized by intermittent, non-pruritic urticarial rash, fevers, arthralgias, myalgias and monoclonal gammopathy, most commonly of the immunoglobulin M (IgM) subtype. Schnitzler’s syndrome should be considered in the differential diagnosis of fever of unknown origin. We report a case of a 56-year-old healthy Caucasian female, who initially presented to the primary care physician’s office with complaints of severe generalized fatigue and myalgias involving thighs and calves. Patient subsequently underwent extensive rheumatologic workup, and was treated with multiple courses of steroids with temporary resolution of symptoms. During the course of her workup she was found to have IgM kappa monoclonal gammopathy, and was referred to hematology for further evaluation. The constellation findings of fever, arthralgias, chronic intermittent non-pruritic urticaria, myalgias, and a negative rheumatologic workup in the presence of IgM monoclonal gammopathy raised the suspicion of Schnitzler’s syndrome. Following completion of additional workup, she was started on anakinra 100 mg daily with prompt resolution of her symptoms. Due to the rarity of the disease, the diagnosis of Schnitzler’s syndrome is often delayed, with an average time to diagnosis being approximately 5 years. The symptoms in most cases can be debilitating and add to significant morbidity as noted in our patient, who required bilateral hip arthroplasty at a much younger age than expected. Published reports discuss the poor quality of life associated with the delayed diagnosis and unawareness of potential end organ damage. With our case report we like to highlight the disease characteristics for an early identification to prevent further organ damage believed to be from chronic inflammation. Early diagnosis and treatment with agents such as interleukin-1 (IL-1) inhibitors can promptly provide symptomatic relief, reduce inflammation and prevent organ damage.

A case of Schnitzler's syndrome without monoclonal gammopathy successfully treated with canakinumab

BACKGROUND

Schnitzler's syndrome (SchS) is a rare autoinflammatory syndrome with diagnostic challenge and be characterized by chronic urticaria, a monoclonal gammopath, periodic fever and bone pain. In addition to the monoclonal gammopathy, bone abnormalities are often found at the site of bone pain in patients with SchS. The remarkable efficacy of interleukin-1 (IL-1) inhibition was also demonstrated in this syndrome.

CASE PRESENTATION

We describe a case of refractory chronic urticaria presenting with clinical manifestations consistent with SchS without monoclonal gammopathy. A 43-year-old female patient suffering from recurring of urticaria with periodic fever as well as bone pain for the past 4 years. The patient had leukocytosis and elevated levels of C-reactive protein (CRP) and serum amyloid A (SAA). PET/CT (positron emission tomography/computed tomography) and MRI (magnetic resonance imaging) examination revealed hyper-metabolism areas in both femoral bone marrow. Although bone marrow histology revealed no abnormality, urticarial skin lesions shows neutrophilic infiltrations without evidence of vasculitis. We could not exclude the possibility of SchS. The patient had been treated with antihistamines, steroids, omarizumab, colchicine and cyclosporine A, no therapeutic effect was observed. She was started on canakinumab 150 mg subcutaneous injection with 4 weeks interval. Within 48 h after the first injection, the urticarial rash disappeared, and febrile attack and bone pain had not recurred. Elevated levels of serum CRP and SAA were normalized within a week after the first injection of canakinumab.

CONCLUSIONS

The current case suggests an important role for IL-1 as a mediator in the pathophysiology of SchS-like refractory urticaria with bine pain. It had been presumed that monoclonal gammopathy may not always present in SchS. It is important to avoid delay in diagnosis and initiation of proper treatment in SchS or autoinflammatory conditions resembling SchS.

Systemic autoinflammatory disease in adults

Systemic autoinflammatory disorders comprise an expanding group of rare conditions. They are mediated by dysfunction of the innate immune system and share a core of phenotypic manifestations including recurrent attacks of fever, cutaneous signs, chest or abdominal pain, lymphadenopathy, vasculopathy, and musculoskeletal symptoms. Diagnosis is often established in childhood, but a growing number of adult patients are being recognized with systemic autoinflammatory disorders, including adult-onset disease. In this review, we provide a concise update on the pathophysiology, clinical presentation, and diagnostic approach of systemic autoinflammatory disorders with an emphasis on the adult patient population. Despite the recent advances in genetic testing, the diagnosis of autoinflammatory disease in adult patients is often based on a thorough knowledge of the clinical phenotype. Becoming acquainted with the clinical features of these rare disorders may assist in developing a high index of suspicion for autoinflammatory disease in patients presenting with unexplained episodes of fever or inflammation.

Schnitzler Syndrome: A Recherche Entity

Schnitzler syndrome (SS) is a rare disease of unknown etiology. Literature suggests that only around 300 well-diagnosed cases have only been reported worldwide and rarely from India. This syndrome has a slight male predominance with a mean age of onset of around 50 years. It is considered an autoinflammatory disease with presentation mimicking adult-onset Still's disease and systemic lupus erythematosus, and its presentation most commonly includes recurrent fever, urticarial rash, arthralgia, and bone pains. The probable pathogenesis is considered to be cytokine-mediated, mostly interleukin- 1 (IL-1), and its association with the NRLP3 gene has been mentioned in a few reports. Herein, we report a case of a 40-year-old female who presented to us with fever, jaundice, rash, and pedal edema, and detailed investigations revealed leukocytosis with low complements, normal bone marrow with an 'M band' in the immunoglobulin M (IgM) region. Skin biopsy was suggestive of leukocytoclastic vasculitis and renal biopsy was suggestive of membranoproliferative glomerulonephritis (MPGN). All autoimmune and viral markers were negative, including cryoglobulins, and by excluding all possible differentials, the diagnosis of Schnitzler syndrome was confirmed. SS is a disease of exclusion and several autoimmune, hematological infections need to be excluded, hence, this requires extensive workup. It's the rarest of rare cases, with a variable presentation, specially pyrexia of unknown origin (PUO) with rash, hence this case will open the physician's vision of undiagnosed cases, and further research will help understand its pathogenesis.

Cytokine Signature in Schnitzler Syndrome: Proinflammatory Cytokine Production Associated to Th Suppression

Background

Schnitzler syndrome (SchS) is a rare autoinflammatory disease characterized by urticarial exanthema, bone and joint alterations, fever and monoclonal IgM gammopathy. Overactivation of the interleukin(IL)-1 system is reported, even though the exact pathophysiological pathways remain unknown.

Objective

To determine ex vivo cytokine profiles of Peripheral Blood Mononuclear Cells (PBMCs) from SchS patients prior to treatment and after initiation of anti-IL-1 therapy (anakinra). The sera cytokine profile was studied in parallel.

Methods

We collected blood samples from thirty-six untreated or treated SchS. PBMCs were cultured with and without LPS or anti-CD3/CD28. Cytokine levels were evaluated in serum and cell culture supernatants using Luminex technology.

Results

Spontaneous TNFα, IL-6, IL-1β, IL-1α, and IL-1RA release by PBMCs of SchS patients were higher than in controls. LPS-stimulation further induced the secretion of these cytokines. In contrast, after T-cell stimulation, TNFα, IL-10, IFNγ, IL-17A, and IL-4 production decreased in SchS patients compared to healthy controls, but less in treated patients. Whereas IL-1β serum level was not detected in most sera, IL-6, IL-10, and TNFα serum levels were higher in patients with SchS and IFNγ and IL-4 levels were lower. Of note, IL-6 decreased after treatment in SchS (p = 0.04).

Conclusion

Our data strengthen the hypothesis of myeloid inflammation in SchS, mediated in particular by IL-1β, TNFα, and IL-6, associated with overproduction of the inhibitors IL-1RA and IL-10. In contrast, we observed a loss of Th1, Th2, and Th17 cell functionalities that tends to be reversed by anakinra.

Rheumatic involvement and bone scan features in Schnitzler syndrome: initial and follow-up data from a single-center cohort of 25 patients

Objective

To report on the characteristics and long-term course of rheumatic manifestations in Schnitzler syndrome (SchS).

Methods

A retrospective cohort study of patients with SchS followed between 2000 and 2020. Inclusion criteria included a diagnosis of SchS (Strasbourg criteria). All available bone scans were reviewed and scored according to the intensity and number of pathological sites. The scintigraphic score was compared with the clinical activity score, CRP level, and treatments.

Results

Twenty-five patients were included. Median age at diagnosis was 68 years. Eighty patients (72%) had SchS-related rheumatic pain. Most patients had a long-standing isolated rash before constitutional and/or rheumatic symptoms appeared. The monoclonal component level was usually very low (IgMκ in 22/25). Rheumatic pain predominated around the knees. Bone scans revealed abnormal tracer uptake in 15/18 (85%). The scintigraphic score correlated with clinical activity (r = 0.4, p < 0.02) and CRP level (r = 0.47, p < 0.01). The scintigraphic score was lower in patients receiving corticosteroids or IL1Ra (interleukin 1 receptor antagonist) than in untreated patients (median scores:2, 0, and 13, respectively; p < 0.05). Two patients developed Waldenström macroglobulinemia. Of the 22 surviving patients, median age at follow-up was 76 years. IL1Ra was used in 13 patients, with dramatic efficacy on both symptoms and bone scan features.

Conclusions

Rheumatic manifestations are very prevalent in SchS. However, bone pain can be misleading and contribute to misdiagnosis. Bone scan abnormalities are very prevalent and correlate with disease activity and treatments. IL1-Ra has a dramatic and durable efficacy but may not be required in every patient early on.

Monoklonale Gammopathie unklarer Signifikanz bei rheumatologischen Erkrankungen

In der rheumatologischen Praxis wird eine monoklonale Gammopathie (MGUS) häufig als Zufallsbefund entdeckt. Meist handelt es sich um einen Laborbefund ohne Krankheitswert, diese Fälle werden als monoklonale Gammopathien unklarer Signifikanz (MGUS) bezeichnet. Für mehrere rheumatisch-entzündliche Systemerkrankungen ist ein erhöhtes Risiko für MGUS bekannt. Aus einer MGUS kann sich ein multiples Myelom, eine primär systemische Amyloidose oder eine andere lymphatische Neoplasie entwickeln. Die relevanten Krankheitsdefinitionen werden genannt und es werden Algorithmen aufgezeigt, um eine monoklonale Gammopathie weiter abzuklären und abhängig vom Progressionsrisiko Verlaufskontrollen vorzunehmen. Die Erkenntnisse darüber, ob rheumatologische Therapien Einfluss auf das Progressionsrisiko haben, sind bislang begrenzt.

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 systemic autoinflammatory disorders for dermatologists. Part 2: disease examples

The systemic autoinflammatory disorders (SAIDS) or periodic fever syndromes are disorders of innate immunity, which can be inherited or acquired. They are almost all very rare and easily overlooked; typically, patients will have seen multiple specialities prior to diagnosis, so a high level of clinical suspicion is key. It is important to note that these are 'high-value' diagnoses as the majority of these syndromes can be very effectively controlled, dramatically improving quality of life and providing protection against the development of irreversible complications such as AA amyloidosis. In Part 1 of this review, we took an overview of SAIDS and described the common features; in this article, we take a more in-depth look at the better recognized or more dermatologically relevant conditions.

A Chinese case series of Schnitzler syndrome and complete remission in one tocilizumab-treated patient

Schnitzler syndrome (SchS) is a rare acquired systemic autoinflammatory disease. The major clinical features of SchS are urticarial rash and monoclonal gammopathy, accompanied by fever, joint pain, and lymphadenopathy. There were few reports about SchS in Chinese population. Herein, we describe two patients with SchS in China and conducted a systematic literature review about SchS. Two Chinese Han patients were diagnosed as SchS in our department from 2017 to 2019. Their phenotype and genotype were carefully documented and studied. We also conducted a systematic literature review about SchS. There was one man (66 years old) and one woman (49 years old). Recurrent fever and urticarial rash occurred in both of them during the febrile attacks and normalized in asymptomatic intervals. Other manifestations included arthralgia, lymphadenopathy, and hearing loss. Hepatic cirrhosis and epilepsy were seen in the male patient. None of them had bone pain or family histories. Serum monoclonal IgM gammopathy was found in both patients. MyD88 gene mutation L258P was identified in the female patient. They were treated with tocilizumab and tripterygium wilfordii Hook F (TwHF) respectively, and both showed good response. The rarity and diversity of SchS make it difficult to be recognized. Anti-IL-6 agents may be alternative therapies when anti-IL-1 therapy is unresponsive or unavailable. Due to the case report, the effect of TwHF in the treatment of SchS should be further studied.

Efficacy and safety of canakinumab treatment in schnitzler syndrome: A systematic literature review

BACKGROUND

Schnitzler syndrome is a rare autoinflammatory disorder characterized by chronic urticarial rash and a monoclonal gammopathy, accompanied by intermittent fever, bone pain, and arthralgia or arthritis. Canakinumab is a fully human monoclonal anti-interleukin-1β (IL-1β) antibody proven to be effective in IL-1 driven autoinflammatory disorders.

METHODS

We systematically searched PubMed and Embase to include all types of studies on canakinumab treatment in Schnitzler syndrome published until March 16, 2020.

RESULTS

Since 2011, 7 publications have been reported on canakinumab treatment in 34 patients with Schnitzler syndrome. The cumulative follow-up was 253 months, and 5 studies had a follow-up duration of 12 months or more. A complete response during treatment was reported in 58.6% of patients; all other patients had a partial response. Two hundred and seven adverse events were reported in 23 patients. Infection (n = 79) was the most common adverse event. One patient died from sepsis due to atypical mycobacterial infection.

CONCLUSION

Based on the results of the current systematic review, canakinumab is an effective long-term treatment with a favorable safety profile in patients with Schnitzler syndrome.

Diagnostic value of 18-F fluorodeoxyglucose PET/CT and bone scan in Schnitzler syndrome

Introduction: Schnitzler syndrome is an auto-inflammatory disease defined by chronic urticarial eruption and monoclonal gammopathy. ¹⁸F fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) is often performed, but its utility in Schnitzler syndrome has not been specifically investigated. The aim of this study was to determine whether PET/CT is informative in the diagnosis and follow-up of Schnitzler syndrome relative to other imaging techniques, including bone scans.Patients and methods: Patients of this study were selected from the French cohort established by Néel et al. All patients with a diagnosis of Schnitzler syndrome (according to Strasbourg's and Lipsker's criteria) who had at least one PET/CT were included. Data were collected from medical records. PET/CT scans were all reviewed by a nuclear physician blinded to the clinical and imaging data.Results: Ten patients underwent at least one PET/CT scan and all had at least one ^99mTechnetium bone scan during their follow-up. The most frequent PET/CT abnormalities were diffuse bone-marrow and/or increased femoral fluorodeoxyglucose uptake, but they did not correlate with disease activity. Conversely, bone-scan abnormalities, including mainly increased radiotracer uptake in long bones, appeared to strongly correlate with Schnitzler syndrome activity.Discussion: PET/CT does not appear to be useful for the diagnosis and follow-up of Schnitzler syndrome. However, bone scans appear to be more sensitive for diagnosis and may correlate with clinical activity. Bone scans may be well positioned to distinguish Schnitzler syndrome relapse from other aetiologies of bone, joint, or muscle pain.Conclusion: Bone scans may be favoured over PET/CT in Schnitzler syndrome.

[Monoclonal gammopathy of undetermined significance and multiple myeloma]

In rheumatological practice monoclonal gammopathy of undetermined significance (MGUS) is a common incidental finding. Several rheumatic inflammatory diseases are known to have an elevated risk of MGUS, which can evolve into multiple myeloma or other lymphatic malignancies. The relevant definitions of disease entities are described, as well as algorithms for further diagnostic work-up and follow-up for monoclonal gammopathy, depending on the risk of progression. Therapeutic strategies against multiple myeloma are presented. Some of these therapeutic modalities could play a future role in treating plasma cell-dominated autoimmune diseases.

Symptomatic patients with P369S-R408Q mutations: familial Mediterranean fever or mixed auto-inflammatory syndrome?

A 51-year-old South African female of Ashkenazi Jewish descent was admitted with acute pleuritic chest pain, shortness of breath, fatigue and fever. She experienced vague abdominal and calf pains for 30 years. Her monozygotic twin was investigated independently for recurrent abdominal pain. Despite initially responding to antibiotics, treating suspected pneumonia, she developed recurrent fevers and pleuritic chest pain. After thorough investigation without significant findings, she re-attended days after discharge with similar symptoms. Familial Mediterranean fever (FMF) was suggested as she met diagnostic criteria and responded to colchicine, though FMF normally presents before 20 years old. Genetic testing showed no pathogenic mutations but heterozygous P369S and R408Q mutations. The significance of these mutations remains unclear, as they are found in asymptomatic patients, suggesting incomplete penetrance. She remains well, with full symptom resolution, but mixed auto-inflammatory syndrome may be a more appropriate diagnosis in symptomatic patients with both P369S and R408Q mutations.

Schnitzler's syndrome - a novel hypothesis of a shared pathophysiologic mechanism with Waldenström's disease

Schnitzler’s syndrome is an auto-inflammatory disorder which is characterized by two mandatory features: an urticarial rash and a monoclonal gammopathy. Although the pathophysiology of this syndrome is not yet fully understood, a role for interleukin-1 seems apparent. While this presumed link between interleukin-1 and the monoclonal gammopathy is not yet elucidated, a mutual factor in pathophysiology however seems likely. Here we present a novel hypothesis of a shared pathophysiologic mechanism between Schitzler’s syndrome and monoclonal gammopathy.

Schnitzler syndrome

Schnitzler syndrome is a very rare acquired systemic disease with many similarities to hereditary autoinflammatory syndromes. The main characteristics are generalized exanthema and IgM monoclonal gammopathy. Other clinical features include fever, muscle, bone, and/or joint pain, and lymphadenopathy. About 15-20% of patients with Schnitzler syndrome develop lymphoproliferative diseases and, in rare cases, amyloid A (AA) amyloidosis can occur if the disease is not treated. Activation of the innate immune system, especially interleukin (IL)-1β, is central to the pathogenesis of disease. Consequently, complete control of disease symptoms can be achieved in 80% of patients by treatment with the IL-1 receptor antagonist anakinra.

Clinical Conditions that Masquerade as Urticaria

Chronic urticaria is one of the most commonly diagnosed dermatoses. Following diagnosis, correct identification and proper treatment significantly reduces disease activity, thereby improving the patient’s quality of life. However, there is an extensive differential diagnosis for chronic urticaria that, if missed, can lead to life-threatening sequelae. Many of the diseases that masquerade as urticaria are rare and often have a significant delay in diagnosis. This paper aims to fill the gap in the literature by clearly characterising the cutaneous eruptions and atypical findings in many of the most common mimickers of chronic urticaria. Conditions such as erythema marginatum seen in conjunction with hereditary angioedema, urticaria vasculitis, autoinflammatory cryopyrin-associated periodic syndromes, adult-onset Still’s disease and systemic onset juvenile arthritis, Schnitzler syndrome, erythema multiforme, and cutaneous mastocytosis will be discussed.

[Schnitzler syndrome]

Schnitzler syndrome is a very rare acquired systemic disease with many similarities to hereditary autoinflammatory syndromes. The main characteristics are generalized exanthema and a monoclonal gammopathy with IgM. Other clinical features include fever, muscle, bone and/or joint pain, and lymphadenopathy. About 15-20% of patients with Schnitzler syndrome develop lymphoproliferative diseases and, in rare cases, amyloid A (AA) amyloidosis can occur if the disease is not treated. Activation of the innate immune system, especially interleukin(IL)-1β, is central in the pathogenesis of the disease. Consequently, complete control of disease symptoms can be achieved in 80% of patients by treatment with the IL-1 receptor antagonist anakinra.

A New Case of Schnitzler Syndrome in Bulgaria

We describe the case of a 74-year-old Bulgarian woman with a long history of chronic urticaria with severe burning sensation, arthralgia and fever. Additional symptoms of Schnitzler such as monoclonal immunoglobulin – kappa component, elevated erythrocyte sedimentation rate and enlarged lymph nodes were detected six years after the onset of the symptoms. The first diagnoses hypersensitive vasculitis and dermatitis were established in 2009. Schnitzler syndrome was recognized and the diagnosis was established 2 years later after some examination tests. The time course of the values of IgM, C-reactive protein, erythrocyte sedimentation rate and neutrophils were presented. The mean value of IgM is 13.8 ± 2.19 g/l, the mean value of erythrocyte sedimentation rate is 48.6 ± 14.46 mm/h and the mean value of C-reactive protein – 29.8 ± 7.34 mg/l. The use of nonsteroid anti-inflammatory drugs throughout the period and corticosteroids prescribed parenterally and orally resulted in the relief of arthralgia and fever.

[Schnitzler syndrome]

Schnitzler syndrome is a very rare acquired systemic disease with many similarities to hereditary autoinflammatory syndromes. The main characteristics are generalized exanthema and a monoclonal gammopathy with IgM. Other clinical features include fever, muscle, bone and/or joint pain, and lymphadenopathy. About 15-20% of patients with Schnitzler syndrome develop lymphoproliferative diseases and, in rare cases, amyloid A (AA) amyloidosis can occur if the disease is not treated. Activation of the innate immune system, especially interleukin(IL)-1β, is central in the pathogenesis of the disease. Consequently, complete control of disease symptoms can be achieved in 80% of patients by treatment with the IL-1 receptor antagonist anakinra.

Mimickers of Urticaria: Urticarial Vasculitis and Autoinflammatory Diseases

A wide differential diagnosis must be considered in a patient presenting with urticarial plaques. Although acute and chronic urticaria are the commonest diagnoses, other differential diagnoses include polymorphous eruption of pregnancy, mast cell disorders, hypereosinophilic syndrome, urticarial vasculitis, pemphigoid, systemic lupus erythematosus, and autoinflammatory disease. This review will specifically address urticarial vasculitis and autoinflammatory syndromes. These entities represent contrasting examples of urticarial-like lesions resulting from either an adaptive immune complex-mediated mechanism (urticarial vasculitis) or an innate immune-mediated mechanism (autoinflammatory disorders), with differing therapeutic implications. In patients presenting with painful, persistent plaques that last more than 24 hours and resolve with bruising of the skin, consideration should be given to a diagnosis of urticarial vasculitis. A biopsy should be obtained to ascertain this diagnosis. In patients presenting with a persistent history of recurrent urticarial plaques associated with signs of systemic inflammation including fevers and elevated inflammatory markers (C-reactive protein [CRP]/serum amyloid A, leukocytosis, and negative connective tissue serologies), consideration should be given to autoinflammatory disorders: the 3 cryopyrin-associated periodic syndromes, Schnitzler syndrome, and familial cold autoinflammatory syndrome 2. Serum protein electrophoresis should be checked to rule out an underlying monoclonal gammopathy.

A Rare but Fascinating Disorder: Case Collection of Patients with Schnitzler Syndrome

Background

Schnitzler syndrome is a rare disorder characterized by a chronic urticarial rash and monoclonal gammopathy (IgM in more than 90% of the cases). It is difficult to distinguish from other neutrophilic urticarial dermatoses, and diagnosis is based on the Strasbourg criteria. Interleukin-1 is considered the key mediator, and interleukin-1 inhibitors are considered first line treatment. Here, we present two cases of Schnitzler syndrome, both successfully treated with anakinra.

Objectives

To increase awareness regarding clinical presentation, diagnosis, and treatment of this rare disorder.

Cases

We describe the clinical features and disease course of two patients with Schnitzler syndrome, diagnosed using the Strasbourg criteria. Both were treated with anakinra with remarkable response to therapy.

Conclusion

Schnitzler syndrome is a rare and underdiagnosed disorder. High suspicion should be maintained in patients with chronic urticaria-like dermatoses, intermittent fevers, and arthralgias. A serum protein electrophoresis and immunofixation should be performed in these patients. The diagnosis is important to recognize as Schnitzler syndrome is associated with malignancy. A lymphoproliferative disorder develops in about 20% of patients at an average of 7.6 years after onset of symptoms. Thus, patients warrant long-term follow-up. IL-1 inhibitors are extremely effective in relieving symptoms and are considered first line therapy.

[Schnitzler syndrome: A review of literature, the authors' observation, and experience with the interleukin-1 inhibitor canakinumab]

The paper reviews the publications dealing with Schnitzler syndrome, a rare autoinflammatory disease, and describes the authors' own clinical observation. It describes the first Russian experience in successfully using the interleukin-1 inhibitor canakinumab to treat this disease.

Kidney involvement in the Schnitzler syndrome, a rare disease

The Schnitzler syndrome (SS) is a rare and underdiagnosed entity that associates a chronic urticarial rash, monoclonal IgM (or sometimes IgG) gammopathy and signs and symptoms of systemic inflammation. During the past 45 years, the SS has evolved from an elusive little-known disorder to the paradigm of a late-onset acquired auto-inflammatory syndrome. Though there is no definite proof of its precise pathogenesis, it should be considered as an acquired disease involving abnormal stimulation of the innate immune system, which can be reversed by the interleukin-1 receptor antagonist anakinra. It clearly expands our view of this group of rare genetic diseases and makes the concept of auto-inflammation relevant in polygenic acquired diseases as well. Increasing numbers of dermatologists, rheumatologists, allergologists, haematologists and, more recently, nephrologists, recognize the SS. The aim of this review is to focus on kidney involvement in the SS. Although the literature regarding kidney involvement in the SS is very poor it can be severe, as in our own case here reported, leading us to recommend the systematic search for nephropathy markers in the SS.