Schnitzler syndrome, an autoimmune–autoinflammatory syndrome: Report of two new cases and review of the literature

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.

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.

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.

The combined prevalence of classified rare rheumatic diseases is almost double that of ankylosing spondylitis

BACKGROUND

Rare diseases (RDs) affect less than 5/10,000 people in Europe and fewer than 200,000 individuals in the United States. In rheumatology, RDs are heterogeneous and lack systemic classification. Clinical courses involve a variety of diverse symptoms, and patients may be misdiagnosed and not receive appropriate treatment. The objective of this study was to identify and classify some of the most important RDs in rheumatology. We also attempted to determine their combined prevalence to more precisely define this area of rheumatology and increase awareness of RDs in healthcare systems. We conducted a comprehensive literature search and analyzed each disease for the specified criteria, such as clinical symptoms, treatment regimens, prognoses, and point prevalences. If no epidemiological data were available, we estimated the prevalence as 1/1,000,000. The total point prevalence for all RDs in rheumatology was estimated as the sum of the individually determined prevalences.

RESULTS

A total of 76 syndromes and diseases were identified, including vasculitis/vasculopathy (n = 15), arthritis/arthropathy (n = 11), autoinflammatory syndromes (n = 11), myositis (n = 9), bone disorders (n = 11), connective tissue diseases (n = 8), overgrowth syndromes (n = 3), and others (n = 8). Out of the 76 diseases, 61 (80%) are classified as chronic, with a remitting-relapsing course in 27 cases (35%) upon adequate treatment. Another 34 (45%) diseases were predominantly progressive and difficult to control. Corticosteroids are a therapeutic option in 49 (64%) syndromes. Mortality is variable and could not be determined precisely. Epidemiological studies and prevalence data were available for 33 syndromes and diseases. For an additional eight diseases, only incidence data were accessible. The summed prevalence of all RDs was 28.8/10,000.

CONCLUSIONS

RDs in rheumatology are frequently chronic, progressive, and present variable symptoms. Treatment options are often restricted to corticosteroids, presumably because of the scarcity of randomized controlled trials. The estimated combined prevalence is significant and almost double that of ankylosing spondylitis (18/10,000). Thus, healthcare systems should assign RDs similar importance as any other common disease in rheumatology.

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.

Phenotype variability of autoinflammatory disorders in the pediatric patient: A pictorial overview

Disruption of innate immunity leading to systemic inflammation and multi-organ dysfunction is the basilar footprint of autoinflammatory disorders (AIDs), ranging from rare hereditary monogenic diseases to a large number of common chronic inflammatory conditions in which there is a simultaneous participation of multiple genetic components and environmental factors, sometimes combined with autoimmune phenomena and immunodeficiency. Whatever their molecular mechanism, hereditary AIDs are caused by mutations in regulatory molecules or sensors proteins leading to dysregulated production of proinflammatory cytokines or cytokine-inducing transcription factors, fever, elevation of acute phase reactants, and a portfolio of manifold inflammatory signs which might occur in a stereotyped manner, mostly with overactivity or misactivation of different inflammasomes. Symptoms might overlap in the pediatric patient, obscuring the final diagnosis of AIDs and delaying the most appropriate treatment. Actually, the fast-paced evolution of scientific knowledge has led to recognize or reclassify an overgrowing number of multifactorial diseases, which share the basic pathogenetic mechanisms with AIDs. The wide framework of classic hereditary periodic fevers, AIDs with prominent skin involvement, disorders of the ubiquitin-proteasome system, defects of actin cytoskeleton dynamics, and also idiopathic nonhereditary febrile syndromes occurring in children is herein presented. Interleukin-1 dependence of these diseases or involvement of other predominating molecules is also discussed.

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.

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.

Skin symptoms as diagnostic clue for autoinflammatory diseases

Autoinflammatory disorders are immune-mediated diseases with increased production of inflammatory cytokines and absence of detectable autoantibodies. They course with recurrent episodes of systemic inflammation and fever is the most common symptom. Cutaneous manifestations are prevalent and important to diagnosis and early treatment of the syndromes. The purpose of this review is to emphasize to dermatologists the skin symptoms present in these syndromes in order to provide their early diagnosis.

Different Therapeutic Paths (Colchicine vs. Anakinra) in Two Patients With Schnitzler's Syndrome

Schnitzler's syndrome is a rare autoinflammatory syndrome with unidentified mechanism of disease and etiology with unknown definitive treatment algorithm. The two obligatory criteria for the diagnosis of Schnitzler's syndrome include chronic urticarial rash and monoclonal gammopathy (immunoglobulin M or immunoglobulin G). In this article, we describe two patients with different courses of disease with different average lengths of time between initial symptoms and the final diagnosis (6 months to 8 years). Exclusion of more common conditions is needed to ensure the correct diagnosis. Treatment strategy depends on the patient's constitutional symptoms (fever, malaise, generalized myalgia, and arthralgias) and laboratory tests of inflammation. Treatment includes usage of conventional drugs and cytokine blockade (interleukin-1 and interleukin-6). Further studies are needed to determine the precise mechanism of disease and the appropriate targeted therapy.

Schnitzler Syndrome Without a Monoclonal Gammopathy: A Case Report

BACKGROUND

Schnitzler syndrome (SS) is a rare autoinflammatory disorder characterized by a recurrent urticarial rash and a monoclonal immunoglobulin M gammopathy, as well as 2 of the following minor criteria: recurrent fever (>38°C), objective signs of abnormal bone remodeling, elevated C-reactive protein level or leukocytosis, and a neutrophilic infiltrate on skin biopsy. Alternatively, a monoclonal immunoglobulin G gammopathy may be present along with 3 minor criteria for diagnosis.

OBJECTIVE

To report a rare case of SS without monoclonal gammopathy and inform physicians of this possible clinical presentation so that treatment is not delayed.

METHODS

We report a case of a 62-year-old white man with a clinical diagnosis of SS without monoclonal gammopathy. He presented with chronic urticaria unresponsive to conventional therapy.

RESULTS AND CONCLUSIONS

To our knowledge, there have only been 3 case reports of SS in the absence of monoclonal gammopathy documented in the literature. SS should be considered based on clinical presentation, even in the absence of monoclonal gammopathy, to facilitate appropriate management.

Schnitzler's syndrome: lessons from 281 cases

Schnitzler’s syndrome is an autoinflammatory disorder characterized by the association of a monoclonal IgM (or IgG) gammopathy, a chronic urticarial rash, and signs and symptoms of systemic inflammation, including fever, arthralgias and bone pain. It was first described in 1972. This review summarizes the clinical features, efficacy of therapies, and follow-up data of the 281 cases that have been reported to date. Also, the results of skin histology, bone imaging, laboratory investigations, and studies of the pathogenesis will be discussed, including the pivotal role of interleukin-1 beta in this disorder.

Autoimmunity and autoinflammation as the yin and yang of idiopathic recurrent acute pericarditis

Autoimmunity and autoinflammation are generally considered as mutually exclusive mechanisms of diseases but may concur to specific syndromes. Idiopathic recurrent acute pericarditis (IRAP) is defined as the recurrence of pericardial symptoms at any point following the prior cessation of acute pericarditis, and the latency is generally 6 weeks. Manifestations of pericarditis such as pericardial friction rub, electrocardiographic changes, and pericardial effusion are less frequent in the subsequent episodes compared to the index attack, and in some cases the only clinical sign is represented by a suggestive chest pain. Several autoimmune diseases may manifest with pericarditis which is often related to viral infections, while postviral pericarditis may in turn display a nonspecific autoimmune background. Similarly, autoinflammatory syndromes such as familial Mediterranean fever and tumor necrosis factor receptor-associated periodic syndrome are characterized by self-limiting pericardial symptoms. Corticosteroids are generally effective, thus supporting the autoimmune nature of IRAP, but dramatic results are obtained with interleukin-1 blocking agents in corticosteroid-dependent cases, pointing to a pathogenic role for the inflammasome. Based on these observations, we submit that IRAP represents a paradigmatic example of the putative coexistence of autoimmunity and autoinflammation: the main aim of this review is to critically discuss the hypothesis as well as the current understanding of this enigmatic clinical condition.

Long-term effectiveness and safety of interleukin-1 receptor antagonist (anakinra) in Schnitzler's syndrome: a French multicenter study

The aim of this study is to assess the long-term effectiveness and safety of IL1Ra in Schnitzler syndrome (SchS). Between 2010 and 2012, we performed a nationwide survey among French internal medicine departments to identify SchS patients. We retrospectively analyzed the long-term efficacy and safety of IL1Ra and the outcome of patients that did not receive this treatment. Forty-two patients were included in the study, 29 of whom received IL1Ra. The mean age at disease onset was 59.9years. Disease manifestations included urticaria (100%), fever (76%), bone/joint pain (86%), bone lesions (76%), anemia (67%), and weight loss (60%). The monoclonal gammopathy was overwhelmingly IgM kappa (83%). The mean follow-up was 9.5years (range: 1.6-35). Two patients developed Waldenström's macroglobulinemia and one developed AA amyloidosis. All of the 29 patients who received IL1Ra responded dramatically. After a median follow-up of 36months (range: 2-79), the effectiveness remained unchanged. All patients remained on anti-IL-1 therapy. Twenty-four patients (83%) went into complete remission and five (17%) into partial remission. Three patients experienced grade 3-4 neutropenia. Six patients developed severe infections. No lymphoproliferative diseases occurred while on IL1Ra. When last seen, all patients without anakinra had an active disease with variable impact on their quality of life. Their median corticosteroids dosage was 6mg/d (range: 5-25). IL1Ra is effective in SchS, with a sharp corticosteroid-sparing effect. Treatment failures should lead to reconsider the diagnosis. Long-term follow-up revealed no loss of effectiveness and a favorable tolerance profile. The long-term effects on the risk of hemopathy remain unknown.

Schnitzler's syndrome: a case report

Schnitzler's syndrome is an extremely rare entity that poses a challenge for the clinician not only due to its difficult diagnosis but also due to its management. In this article we report a new case and briefly review the current treatment options.

Schnitzler's syndrome: diagnosis, treatment, and follow-up

Schnitzler's syndrome is characterized by recurrent urticarial rash and monoclonal gammopathy, associated with clinical and biological signs of inflammation and a long-term risk of AA amyloidosis and overt lymphoproliferation. An extensive literature review was performed, and the following questions were addressed during an expert meeting: In whom should Schnitzler's syndrome be suspected? How should the diagnosis of Schnitzler's syndrome be established? How should a patient with Schnitzler's syndrome be treated? How should a patient with Schnitzler's syndrome be followed up?. A diagnosis of Schnitzler's syndrome is considered definite in any patient with two obligate criteria: a recurrent urticarial rash and a monoclonal IgM gammopathy, and two of the following minor criteria: recurrent fever, objective signs of abnormal bone remodeling, elevated CRP level or leukocytosis, and a neutrophilic infiltrate on skin biopsy. It is considered probable, if only 1 minor criterion is present. In patients with monoclonal IgG gammopathies, diagnosis is definite if three minor criteria are present and possible if two are present. First-line treatment in patients with significant alteration of quality of life or persistent elevation of markers of inflammation should be anakinra. Follow-up should include clinical evaluation, CBC and CRP every 3 months and MGUS as usually recommended.

Autoinflammation: From monogenic syndromes to common skin diseases

Autoinflammation is characterized by aberrant regulation of the innate immune system and often manifests as periodic fevers and systemic inflammation involving multiple organs, including the skin. Mutations leading to abnormal behavior or activity of the interleukin 1 beta (IL-1ß)-processing inflammasome complex have been found in several rare autoinflammatory syndromes, for which anticytokine therapy such as IL-1 or tumor necrosis factor-alfa inhibition may be effective. It is becoming clear that features of autoinflammation also affect common dermatoses, some of which were previously thought to be solely autoimmune in origin (eg, vitiligo, systemic lupus erythematosus). Recognizing the pathogenetic role of autoinflammation can open up new avenues for the targeted treatment of complex, inflammatory dermatoses.

Clinical and histopathologic review of Schnitzler syndrome: the Mayo Clinic experience (1972-2011)

BACKGROUND

Schnitzler syndrome is a rare multisystem disorder, defined by urticaria and monoclonal gammopathy, that is associated with malignancy. Considered a neutrophilic urticarial dermatosis, previous reports have included patients with leukocytoclastic vasculitis.

OBJECTIVE

We sought to better define the clinical features, histopathology, and outcomes of Schnitzler syndrome.

METHODS

We retrospectively reviewed clinical records and cutaneous histopathology of all patients with Schnitzler syndrome seen at our institution from January 1, 1972, through July 31, 2011.

RESULTS

Of the 20 patients identified, 80% had IgM κ monoclonal gammopathy; others had IgG λ (10%), IgG κ (5%), or IgM κ+λ (5%). Patients had fevers (85%), arthralgias (70%), leukocytosis (70%), increased erythrocyte sedimentation rate (70%), bone pain (50%), lymphadenopathy (40%), and organomegaly (5%); 45% developed a hematologic malignancy. Histopathologic examination (n = 14) showed predominantly neutrophilic perivascular and interstitial inflammation (57%) or predominantly mononuclear cell perivascular inflammation (29%), with eosinophils in 50% of cases. None showed leukocytoclastic vasculitis.

LIMITATIONS

Our study was limited by its retrospective design.

CONCLUSION

We added 20 patients to approximately 100 reported cases of Schnitzler syndrome. Neutrophilic urticarial dermatosis was the most common histopathologic pattern, but mononuclear cells were predominant in many cases and the infiltrates often contained eosinophils. A high index of suspicion and careful clinicopathologic correlation are needed to avoid diagnostic delays in this syndrome associated with hematologic malignancy.

The fresco of autoinflammatory diseases from the pediatric perspective

Autoinflammatory diseases are genetic or acquired clinical entities globally caused by the aberrant release of the proinflammatory cytokine interleukin-1 and mostly characterized by recurrent spontaneous inflammatory events which do not produce antigen-specific T cells or autoantibodies. Within the past decade, the list of autoinflammatory diseases has included cryopyrin-associated periodic syndromes, familial Mediterranean fever, mevalonate kinase deficiency, tumor necrosis factor receptor-associated periodic syndrome, hereditary pyogenic disorders, pediatric granulomatous autoinflammatory diseases, idiopathic febrile syndromes, complement dysregulation syndromes and Behçet's disease. Most of these conditions interact with the inflammasomes, intracellular molecular complexes coordinating the phylogenetically ancient response of the innate immune system. The pathogenetic mechanisms of these diseases have shown the evidence of disrupted interleukin-1 signaling for most of them and allowed to locate interleukin-1 as an attractive therapeutic target. The whole fresco of autoinflammatory diseases in pediatrics will be discussed in this review with the aim of establishing both diagnostic clues and treatments for each condition.