Schnitzler Syndrome: Insights into Its Pathogenesis, Clinical Manifestations, and Current Management.

Schnitzler syndrome is a rare disorder characterized by a chronic urticarial rash associated with immunoglobulin M (IgM) monoclonal gammopathy. Schnitzler syndrome shares strong clinicopathologic similarities with monogenic IL-1-mediated autoinflammatory disorders and is now considered an acquired adult-onset autoinflammatory disease. The spectacular effect of interleukin-1 inhibitors demonstrates the key role of this cytokine in the pathogenesis of the disease. However, the physiopathology of Schnitzler syndrome remains elusive, and the main question regarding the relationship between autoinflammatory features and monoclonal gammopathy is still unanswered. The purpose of this narrative review is to describe what is currently known about the pathogenesis of this peculiar disease, as well as to address its diagnosis and management.

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.

Neutrophilic Urticarial Dermatosis.

Neutrophilic urticarial dermatosis (NUD) is a rare form of dermatosis that is poorly understood. It was first described by Kieffer and colleagues as an urticarial eruption that is histopathologically characterized by a perivascular and interstitial neutrophilic infiltrate with intense leukocytoclasia and without vasculitis or dermal edema. NUD clinically presents as a chronic or recurrent eruption that consists of nonpruritic macules, papules, or plaques that are pink to reddish and that resolve within 24 hours without residual pigmentation. NUD is often associated with systemic diseases such as Schnitzler syndrome, lupus erythematosus, adult-onset Still's disease, and cryopyrin-associated periodic syndromes.

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.

Schnitzler syndrome refractory to anakinra: successful treatment with canakinumab.

Schnitzler syndrome (SchS) is a rare autoimmune and inflammatory disease mediated by interleukin-1 beta (IL-1ß). Recurrent monoclonal gammopathy and chronic urticarial rash are the symptoms required for diagnosis according to the Strasbourg criteria. The low prevalence of this syndrome (around 300 cases have been reported) and confusion with other inflammatory disorders may delay the diagnosis for up to 5 years. Although the most effective treatment for SchS is anakinra, some patients do not respond to this treatment. We report a case of SchS in a 64-year-old woman with multiple episodes of fever, severe rash, erythema, arthralgia and dyspnea. The patient was successfully treated with canakinumab after anakinra intolerance and failure of colchicine, prednisone, methotrexate and dapsone. After the first dose of canakinumab the skin wounds rapidly improved and the patient did not require any concomitant treatments. The cause of SchS is still unknown and a differential diagnosis is recommended, especially with adult-onset Still´s disease due to their similar symptoms. Canakinumab, a specific anti-IL-1ß antibody, blocks its binding to receptors, thereby preventing IL-1ß-induced gene activation and production of inflammatory mediators. Canakinumab has proven to be an effective drug in SchS, providing an alternative to anakinra.

Schnitzler syndrome.

A woman in her late 40s with a history of psoriatic arthritis presented to us with fever, migratory rash, cervical and axillary lymphadenopathy, and generalised myalgia. Her symptoms did not improve with steroids and her inflammatory markers were in the range of 200 mg/dL for C-reactive protein, erythrocyte sedimentation rate of 71 mm/hour and ferritin of 4000 ng/mL. Infectious workup was negative. Haematological malignancy and autoimmune conditions were among the top differentials, and she was eventually diagnosed with Schnitzler syndrome. A multidisciplinary team consisting of internal medicine, rheumatology, infectious disease and haematology-oncology specialists was involved in the care of this patient. We highlight the diagnostic schema that was followed for this rare and unique constellation of symptoms.

An unusual presentation of immunoglobulin A gammopathy in a patient with Schnitzler's syndrome.

This case summarizes a 69-year-old woman who presented with a history of recurrent fevers, widespread urticarial rash and generalized myalgias for several years with an eventual diagnosis of Schnitzler's syndrome. This is a rare autoinflammatory condition which typically involves a chronic urticarial rash, monoclonal immunoglobulin M (IgM) or IgG gammopathy. Rapid improvement in above symptoms were noted with anakinra, an interleukin-1 receptor antagonist. We report an unusual case of a 69-year-old woman who presented with an isolated IgA monoclonal gammopathy.

Case report: Schnitzler-like syndrome without monoclonal gammopathy.

Schnitzler syndrome is a rare autoinflammatory disorder characterized by urticarial rash, joint pain, recurrent fever, leucocytosis, elevated C-reactive protein (CRP) and serum amyloid A (SAA), and monoclonal IgM or IgG gammopathy. According to the Strasbourg criteria, both urticarial rash and gammopathy are mandatorily required for the diagnosis of Schnitzler's syndrome. However, incomplete variants lacking either skin symptoms or monoclonal gammopathy have also been described. Here, we report a case in which the diagnosis of Schnitzler-like syndrome was made despite the absence of gammopathy, based on neutrophilic dermal inflammation, episodic and excessive increase in inflammatory parameters, and prompt response to anakinra, a soluble IL1 receptor antagonist (sIL-1RA). In addition, we detected neutrophil epitheliotropism, which is highly suggestive of autoinflammatory disease. Using whole-exome sequencing, we were unable to find a causative pathogenic mutation but did find several mutations possibly related to the inflammatory processes in this patient. This and other cases highlight that the existing Strasbourg criteria are too strict to capture Schnitzler-like syndromes that may respond well and rapidly to IL1 inhibition. Recurrent episodes of disease with normalization of inflammatory symptoms in the interval, rapid response to anakinra, and neutrophilic epitheliotropism in a lesional skin biopsy may help confirm the diagnosis of Schnitzler-like syndrome.

Summary of the current status of clinically diagnosed cases of Schnitzler syndrome in Japan.

BACKGROUND: Schnitzler syndrome is a rare disorder with chronic urticaria, and there is no report summarizing the current status in Japan. METHODS: A nationwide survey of major dermatology departments in Japan was conducted in 2019. We further performed a systematic search of PubMed and Ichushi-Web, using the keywords "Schnitzler syndrome" and "Japan" then contacted the corresponding authors or physicians for further information. RESULTS: Excluding duplicates, a total of 36 clinically diagnosed cases were identified from 1994 through the spring of 2022, with a male to female ratio of 1:1. The median age of onset was 56.5 years. It took 3.3 years from the first symptom, mostly urticaria, to reach the final diagnosis. The current status of 30 cases was ascertained; two patients developed B-cell lymphoma. SchS treatment was generally effective with high doses of corticosteroids, but symptoms sometimes recurred after tapering. Colchicine was administered in 17 cases and was effective in 8, but showed no effect in the others. Tocilizumab, used in six cases, improved laboratory abnormalities and symptoms, but lost its efficacy after several years. Rituximab, used in five cases, was effective in reducing serum IgM levels or lymphoma mass, but not in inflammatory symptoms. Four cases were treated with IL-1 targeting therapy, either anakinra or canakinumab, and achieved complete remission, except one case with diffuse large B-cell lymphoma. CONCLUSIONS: Since Schnitzler syndrome is a rare disease, the continuous collection and long-term follow-up of clinical information is essential for its appropriate treatment and further understanding of its pathophysiology.

Case report: Successful treatment with tofacitinib and colchicine in a patient with Schnitzler syndrome.

We report a case of late-onset Schnitzler syndrome successfully treated with Janus-activated kinase (JAK) inhibitors and colchicine. Schnitzler syndrome should be considered for recurrent chronic urticaria when accompanied by fever, fatigue, rapid weight loss, and poor response to antihistamine treatment. Skin biopsy, bone marrow biopsy, and electrophoresis help confirm the diagnosis. Early diagnosis and treatment can lead to complete resolution of symptoms. Besides interleukin (IL)-1 and IL-6 inhibitors, JAK inhibitors and colchicine may be considered as other choices of treatment.

Schnitzler Syndrome Presenting as a Fever of Unknown Origin with Elevated Alkaline Phosphatase Levels.

Schnitzler syndrome (SchS) is a rare, acquired, autoinflammatory disease that is sometimes associated with a fever of unknown origin (FUO). Elevated alkaline phosphatase (ALP) stemming from abnormal bone remodeling is a characteristic laboratory finding of SchS and is included in the diagnostic criteria. However, its utility as a clue to the diagnosis of SchS has been under-emphasized. We herein report a case of SchS presenting with a FUO and highly elevated ALP concentration, which led to repeated, unnecessary liver biopsies.

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.

A man in his fifties with recurrent urticaria, fever and joint pain. / En mann i 50-årene med tilbakevendende urtikaria, feber og leddsmerter.

BACKGROUND: Schnitzler's syndrome is a rare, acquired and probably underdiagnosed disorder. It is a type of autoinflammatory condition with late onset. CASE PRESENTATION: A man in his fifties had had recurrent urticaria, fever and chronic joint pain during the previous year. After an extensive investigation, no evidence of infection, autoimmune disease or malignancy was found. Blood samples showed moderately elevated SR and CRP, mild thrombocytosis and presence of monoclonal IgM in low concentration (MGUS). The combination of sterile inflammation, joint/muscle pain, urticaria and M-component was consistent with Schnitzler's syndrome. He was placed on a treatment trial with anakinra (interleukin [IL]-1 receptor antagonist) 100 mg x 1 daily, given as a subcutaneous injection. His condition was excellent until one week after the first injection. The initial treatment indicated a good clinical effect of IL-1 blockade, but due to the very unpleasant localised side effects (extensive dermatitis), treatment with anakinra was withdrawn, and canakinumab (monoclonal antibody against IL-1ß) was chosen instead. He responded very well to this treatment and experienced no adverse effects. One year after starting treatment, the patient still has an excellent treatment response. INTERPRETATION: Anakinra is the treatment of first choice for this condition, but this case history illustrates that canakinumab can be tried if anakinra is not tolerated by the patient.

Retention rate of IL-1 inhibitors in Schnitzler's syndrome.

OBJECTIVES: Schnitzler's syndrome is a rare autoinflammatory disease. Clinical response to IL-1 inhibitor drugs has been described, but limited information is available on the long-term efficacy and safety of these agents in Schnitzler's syndrome. METHODS: A retrospective study was conducted of patients with Schnitzler's syndrome fulfilling Strasbourg diagnostic criteria followed in 9 Italian centres. The retention rate of IL-1 inhibitors was evaluated using Kaplan-Meier analysis. RESULTS: Fifteen of 20 patients with Schnitzler's syndrome were treated with IL-1 inhibitors: in total, they received 16 courses of anakinra (median duration 20.0 months [6.0-58.3]), and 8 courses of canakinumab (median duration 19.0 months [13.5-31.0]). The retention rate of IL-1 inhibitors was 73.4% [SE 9.4] at 1 year and 63.6% [SE 10.4] at 2 years. There was no significant difference between the retention rate of anakinra and canakinumab. The retention rate was higher in patients with a definite diagnosis according to the Strasbourg criteria as compared with those with a probable diagnosis (p=0.03). At the last follow-up visit, all patients who started therapy with IL-1 inhibitors were still on treatment, although in some cases with an increased dosage compared to the start of therapy. A sparing effect on the use of conventional synthetic disease-modifying anti-rheumatic drugs and a significant reduction of prednisone dosage (p=0.02) and of serum amyloid A (SAA) levels (p=0.03) were observed. CONCLUSIONS: The retention rate of IL-1 inhibitors in patients with Schnitzler's syndrome was high, particularly in patients with a definite diagnosis according to the Strasbourg criteria, reflecting their effectiveness in the treatment of this syndrome.

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)-1ß. 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-1ß or IL-6 prevents conversion to a hematopoietic disorder, further collection of cases and long-term follow-up will be needed.