Neutrophilic urticarial dermatosis: a variant of neutrophilic urticaria strongly associated with systemic disease. Report of 9 new cases and review of the literature

Neutrophilic Urticarial Dermatosis: A Window into Systemic Inflammation and Autoimmune Disorders

Neutrophilic urticarial dermatosis (NUD) is a distinctive dermatological manifestation that is commonly associated with systemic autoinflammatory and autoimmune diseases. This review comprehensively explores NUD in the context of five major conditions: Schnitzler syndrome, Still's disease, cryopyrin-associated periodic syndrome, systemic lupus erythematosus, and VEXAS syndrome. For each condition, a detailed discussion of the underlying mechanisms, clinical presentations, diagnostic criteria, and treatment strategies is provided. In addition, cases exhibiting features similar to NUD are emphasized, with a comprehensive examination of the pathological characteristics, particularly focusing on neutrophilic epitheliotropism. This review underscores the significance of identifying NUD as a potential indicator of systemic autoimmune disorders and discusses the role of skin biopsy and laboratory tests in diagnosing the underlying etiology. Finally, a diagnostic framework for NUD is proposed, highlighting the importance of a multidisciplinary assessment to ascertain the underlying systemic condition responsible for the dermatological manifestations. The objective of this review is to enhance the comprehension of NUD, thereby facilitating early diagnosis and the implementation of targeted strategies for affected patients.

Conceptual Contextualization of Neutrophilic Dermatoses

ABSTRACT

Neutrophilic dermatoses are defined as inflammatory skin diseases characterized by sterile infiltration of polymorphonuclear neutrophils into various cutaneous layers. Although, in many cases, neutrophilic dermatoses represent the cutaneous counterpart of autoinflammatory diseases, this is not always the case, and there are other causes associated with this group of diseases, such as the administration of certain drugs or an underlying tumor. However, understanding the autoinflammatory context in which most of these entities develop, as well as their close relationship with autoimmunity, is key to comprehending their pathogenesis. In addition, understanding the mechanisms by which neutrophils migrate to the dermis and become activated is fundamental for interpreting the morphological findings of these biopsies. Finally, the description of a new group of neutrophilic dermatoses in recent years, in relation to keratinization disorders, has been crucial for understanding the best therapeutic approach for these difficult-to-manage entities.

Histopathologic Features in Urticaria and Urticarial Variants: Plasma Cells Should Be Rare

INTRODUCTION

Urticaria is a common cutaneous reaction pattern characterized by clinically transient edematous papules and wheals. Microscopically, intensity and predominant inflammatory cell type can vary, including lymphocytes, eosinophils, neutrophils, and mast cells. Plasma cells are rarely described within the infiltrate of urticaria, but systematic study to evaluate the frequency of this finding is lacking.

MATERIALS AND METHODS

The institutional dermatopathology archive was searched for 2018-2023 to identify cases diagnosed as urticaria and urticarial variants; 58 consecutive cases were included. Study authors, including one board-certified dermatopathologist, evaluated H&E slides for variation in inflammatory cells present, inflammation density/distribution, and predominant cell types.

RESULTS

Fifty-eight cases (female: 39, male: 19) were reviewed. Eleven cases (19%) showed rare, scattered plasma cells (0.02-0.09/mm2). Other inflammatory cell types predominated and, like other studies, fell into lymphocytic and neutrophilic predominant categories. Inflammation density predominantly ranged from sparse to moderate, with only two cases having brisk inflammation.

CONCLUSION

This study highlights that rare plasma cells may be present in urticaria biopsies but should not be abundant or clustered.

Investigator-initiated, multi-center, single-arm, open-label study of the effectiveness of canakinumab in Japanese patients with Schnitzler syndrome

BACKGROUND

Schnitzler syndrome is an adult-onset autoinflammatory disease characterized by an urticaria-like rash and monoclonal gammopathy with fever and fatigue. Although some treatments have shown efficacy in clinical trials, no approved treatment exists. We aimed to assess canakinumab, an anti-IL-1β monoclonal antibody, in Japanese patients.

METHODS

This phase II, multicenter, single-arm, open-label study enrolled five patients with active disease from four hospitals. Patients received a single subcutaneous dose of canakinumab 150 mg. The primary endpoint was the proportion of patients achieving a complete clinical response (CR), based on physician global assessment on Day 7. If a CR was not achieved on Day 7 or by 8 weeks post-treatment, the dose was increased to 300 mg. Dosing continued every 8 weeks until 24 weeks. The study also evaluated patient-reported disease activity and changes in acute inflammatory markers, including white blood cell count, neutrophil count, C-reactive protein concentration, and serum amyloid A level. Quality of life was assessed using the Dermatology Life Quality Index and the 36-item Short Form health survey. Safety was also evaluated.

RESULTS

Sixty percent (3/5) of patients had a CR on Day 7. One of the remaining two patients had a CR 7 days after the dose was increased to 300 mg. All five patients, including those who did not achieve a CR, showed improvement in inflammatory markers and quality of life scores, and no new adverse events were detected.

CONCLUSIONS

In this trial, canakinumab showed a potential for usefulness in Japanese patients with Schnitzler syndrome.

Background and Clinical Features of a Unique and Mysterious Autoinflammatory Disease, Schnitzler Syndrome

Schnitzler syndrome is a unique autoinflammatory disease, of which 747 cases have been described worldwide to date. The main features of the syndrome are a triad of recurrent urticaria, monoclonal IgM gammopathy, systemic inflammation associated with recurrent fever, joint and bone pain, and atypical bone remodeling (osteosclerosis). The abnormal activation of the NLRP3 inflammasome produces IL-1, which drives the disease pathology, but it also involves IL-6 and IL-18. Unlike other autoinflammatory diseases, Schnitzler syndrome lacks evidence of the gene divergence causing the abnormal activation of NLRP3. However, mutations in the MEFV and MYD88 genes can be associated with the development of the disease. Due to its rarity, diagnosing the disease can be a challenging task. IL-1 inhibitors (i.e., anakinra, canakinumab, and rilonacept) are prominent in the treatment of the disease, but the IL-6 receptor inhibitor tocilizumab and the Bruton's tyrosine kinase inhibitor ibrutinib are also promising alternatives. In this summary article, we aim to provide a comprehensive overview of the clinical and molecular background of the disease and potential therapeutic targets, based on the cases reported so far. We diagnosed a patient who, to the best of our knowledge, represents the 748th documented case of this specific pathology. In the context of this patient, we would also like to draw attention to the potential pathogenic role of two novel gene mutations (variants of the MEFV gene "c.2084A>G" and the F2 gene "3'UTR c.*97G>A").

Neutrophilic urticarial dermatosis without systemic disease: case report

Neutrophilic urticarial dermatosis (NUD) is an uncommon and not well understood disease. We report a 24-year-old female with persistent present with pruritic and painful urticarial plaques unresponsive to convential treatment. Histopathologically, it demonstrates a perivascular and interstitial neutrophilic infiltrate with leukocytoclasia without evidence of vasculitis or dermal edema consistent with neutrophilic urticarial dermatosis. Further investigations to rule out underlying autoimmune, autoinflammatory and gentic systemic disease were negative. Furthermore, the cutaneous eruption was resistant to multiple therapeutic interventions including colchicine and dapsone treatment, and show significant response to treatment with anakinra, interleukin-1 receptor antagonist. Based on literature review, the case reported here is the second case with clinical and pathologic features of NUD without systemic disease and the first case of NUD that showed resistant to colchicine and dapsone treatment, with adequate response to anakinra.

The Histopathology of Vacuoles, E1 Enzyme, X-Linked, Autoinflammatory, Somatic Syndrome: Report of 12 Skin Biopsies From 6 Patients

ABSTRACT

We present the histopathology of 12 skin biopsies from 6 patients with vacuoles, enzyme E1, X-linked, autoinflammatory, somatic syndrome and review the literature. The age of these 6 men ranges from 62 to 83 years (median of 70 years). UBA1 mutation was documented in all 6 patients. Multiple organ systems were involved with constitutional symptoms noted in 4 of 6 patients (67%), cutaneous involvement in 6 of 6 patients (100%), hematologic abnormalities in 6 of 6 patients (100%), pulmonary involvement in 4 of 6 patients (67%), musculoskeletal abnormalities in 3 of 6 patients (50%), vascular thrombosis in 2 of 6 patients (33%), ocular involvement in 2 of 6 patients (33%), and gastrointestinal involvement in 5 of 6 patients (83%). Of the 6 presented patients, neutrophilic dermatosis was seen in 3 biopsies, histiocytoid neutrophilic dermatosis in 1 biopsy, neutrophilic dermatosis with vasculitis in 1 biopsy, neutrophilic and granulomatous dermatitis in 2 biopsies, septal panniculitis consistent with erythema nodosum in 2 biopsies, and nonspecific patterns in 3 biopsies. In summary, neutrophilic dermatosis, small-vessel vasculitis, and panniculitis are frequent histopathologic patterns noted in decreasing frequency in skin biopsies of the patients with vacuoles, enzyme E1, X-linked, autoinflammatory, somatic syndrome. However, the histopathologic findings can be diverse, nonspecific in some instances, and varied among different biopsies obtained from the same patient.

Dapsone Use in Dermatology

Dapsone, initially synthesized for textile dyeing, gained recognition in the 1930s for its antibacterial properties, leading to its utilization in dermatology for leprosy and dermatitis herpetiformis. Despite US Food and Drug Administration (FDA) approval for these conditions, dapsone's off-label uses have expanded, making it a valuable option in various dermatologic conditions. This review seeks to highlight the common uses of dapsone in its FDA indications and off-label indications. Diseases in which dapsone is considered first-line therapy or adjunctive therapy are reviewed, with highlights from the resources included. An overview of dapsone's pharmacokinetics, pharmacodynamics, indications, dosages, and safety profile are also reviewed. Dapsone's versatility and safety profile make it a cost-effective treatment option in dermatology, particularly for patients with limited access to specialized medications. Ongoing clinical trials are also described exploring dapsone's efficacy in novel dermatologic uses. Dapsone has been a valuable adjunctive therapy across various dermatologic conditions for years and evidence for its use continues to expand.

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.

Neutrophilic epitheliotropism, proposed as an auto-inflammatory condition of neutrophilic urticarial dermatosis including Schnitzler syndrome, is also observed in Japanese cases

Schnitzler syndrome (SchS) is a rare autoinflammatory disease characterized by bone pain, recurrent fever, leukocytosis, and elevated C-reactive protein, along with an urticaria-like rash and monoclonal immunoglobulin (Ig)M or IgG gammopathy. Notably, the condition is distinguished by a relatively persistent recurrent urticarial-like rash. Histopathological features observed in the skin comprise diffuse neutrophil infiltration into the dermis, absence of dermal edema, and vascular wall degeneration, all of which classify SchS as a neutrophilic urticarial dermatosis (NUD). Accumulated histological data from skin biopsies of patients with NUD have revealed a sensitive histopathological marker for NUD, acknowledged as neutrophilic epitheliotropism, which has been proposed as reflecting an autoinflammatory condition. In this report, we present three SchS patients: two men (ages 55 and 68) and a woman (age 75), all displaying neutrophilic epitheliotropism in their skin biopsy specimens. Additionally, a review of eight previously reported SchS cases in Japan identified neutrophilic epithliotropism in five cases. These findings suggest that the inclination of neutrophils toward the epithelial tissue could aid in confirming diagnoses of NUD in most cases that need to be differentiated from conventional urticaria. Consequently, we emphasize that acknowledging neutrophilic epithelial predilection as a hallmark of NUD is critical for expediting early diagnosis and appropriate treatment for SchS.

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.

Role of neutrophils in cutaneous lupus erythematosus

There are various types of cutaneous lupus erythematosus (CLE), either with or without the association of systemic lupus erythematosus (SLE). In some of the subtypes of cutaneous lupus, histopathology reveals neutrophil infiltration in the lesional skin; however, the significance of neutrophils in CLE is not yet fully elucidated. Recent studies have shown that neutrophil extracellular traps (NETs) formation by activated neutrophils is observed in several types of CLE, including lupus panniculitis, subacute lupus erythematosus, and acute lupus erythematosus, although the number of reports is small. Excessive NETosis, due to either increased NETs formation or defective clearance of NETs, may play a role in the induction of autoimmunity and autoantibody production in SLE, as well as endothelial damage, thrombus formation, and vascular damage in the lesional skin. CLE is an excessive interferon-driven autoimmune disease. Plasmacytoid dendritic cells are located in lupus erythematosus skin and contribute to the etiology of skin lesions as a main producing cell of type I interferon. Neutrophils, monocytes, and keratinocytes also produce type I interferon via several triggers. Neutrophils play an important role in the innate immune response in SLE. In this review, several types of CLE with neutrophil infiltration, as well as the role of neutrophils are discussed.

Annular neutrophilic dermatoses

Neutrophilic dermatoses (NDs) constitute a group of diseases characterized by sterile neutrophilic infiltrations. Many NDs usually present with infiltrated erythematous plaques, nodules, urticarial plaques, or pustules. Lesions may show variability, and atypical presentations may develop among NDs. Annular lesions have been reported in many NDs and may lead to diagnostic problems. Clinical features and histopathologic findings such as localization of the neutrophilic infiltrate, existence of other cell types, and absence of true vasculitis may be helpful to distinguish NDs. Some of these NDs are associated with infections, inflammatory diseases, and malignancies. In most NDs, systemic steroids and dapsone are very effective and usually first choices. Colchicine, antimicrobials such as doxycycline, tetracycline, and sulfapyridine, and other immunosuppressants such as cyclosporin, methotrexate, and mycophenolate mofetil have been used successfully in treating many NDs. Tumor necrosis factor α inhibitors have also been used successfully in treating many NDs. Janus kinase inhibitors are effective in CANDLE (chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperature) syndrome, anakinra in neutrophilic urticarial dermatosis, and intravenous immunoglobulin in resistant pyoderma gangrenosum. We discuss the diagnosis and management of NDs that may present with annular lesions.

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.

Cutaneous involvement in VEXAS syndrome: clinical and histopathologic findings

BACKGROUND

VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome is an autoinflammatory disease with frequent cutaneous manifestations.

METHODS

We conducted a retrospective study of all patients with genetically confirmed VEXAS syndrome seen at our institution. Available clinical photographs and skin biopsy slides were reviewed.

RESULTS

Cutaneous manifestations developed in 22/25 (88%) patients with VEXAS syndrome. From this group, 10/22 (45%) developed skin involvement before or at the time of other clinical features of VEXAS. Twenty distinct dermatologic presentations of VEXAS from 14 patients were reviewed, and histopathologic patterns were classified as follows: neutrophilic urticarial dermatosis (n = 5, 25%), leukocytoclastic/urticarial vasculitis (n = 4, 20%), urticarial tissue reaction (n = 4, 20%), neutrophilic dermatosis (n = 3, 15%), neutrophilic panniculitis (n = 2, 10%), and nonspecific chronic septal panniculitis (n = 2, 10%). Common systemic findings included macrocytic anemia (96%), fever (88%), thrombocytopenia (76%), weight loss (76%), ocular inflammation (64%), pulmonary infiltrates (56%), deep venous thrombosis or pulmonary embolism (52%), and inflammatory arthritis (52%).

CONCLUSIONS

Cutaneous involvement is a common feature of VEXAS syndrome, and histopathologic findings exist on a spectrum of neutrophilic inflammatory dermatoses.

Adalimumab Biosimilar-Induced Autoimmunity-Related Sweet-Like Neutrophilic Dermatosis

ABSTRACT

Antitumor necrosis factor therapies have shown to produce a broad range of cutaneous eruptions. We report the case of a patient under adalimumab biosimilar treatment for a punctate inner choroidopathy who developed a cutaneous eruption on sun-exposed areas that showed a diffuse dermal neutrophilic infiltrate consistent with a Sweet-like neutrophilic dermatosis and some features of autoimmunity.

Autoimmunity-related neutrophilic dermatosis after coronavirus disease 2019 vaccination: A case report and literature review

Autoimmune diseases triggered by coronavirus disease 2019 (COVID-19) mRNA vaccination have been emerging. Here, we report the case of a 27-year-old Japanese man with autoimmunity-related neutrophilic dermatosis, occurring as an initial cutaneous manifestation of systemic lupus erythematosus with Sjögren syndrome after the second dose of the Pfizer/BioNTech COVID-19 vaccination. The patient presented with urticarial erythema and partially annular erythema on the trunk and extremities with severe pruritus. Histopathological analysis showed vacuolar degeneration at the dermo-epidermal junction and interstitial neutrophil infiltration. We reviewed eight patients, including the aforementioned patient, with exacerbation or new-onset of SLE after COVID-19 vaccination and found the patient had relatively mild symptoms, itchy annular erythema, and positive anti-SS-A/SS-B antibodies. COVID-19 mRNA vaccination can induce the production of type-I interferon, which plays a crucial role in the pathogenesis of SLE and may cause autoimmunity-related neutrophilic dermatosis in susceptible individuals. In the case that itchy annular erythema develops approximately 2 weeks after the vaccination, the possibility of systemic or cutaneous lupus erythematosus should be considered. For an accurate diagnosis, dermatologists should obtain a recent vaccination history and perform complete antibody profiling and skin biopsy for patients presenting with annular or erythema multiforme-like lesions.

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.

Improving Diagnosis and Clinical Management of Acquired Systemic Autoinflammatory Diseases

Systemic autoinflammatory diseases (SAID) are conditions caused by dysregulation or disturbance of the innate immune system, with neutrophils and macrophages the main effector cells. Although there are now more than 40 distinct, genetically defined SAIDs, the genetic/molecular diagnosis remains unknown for a significant proportion of patients with the disease onset in adulthood. This review focuses on new developments related to acquired/late onset SAID, including phenocopies of monogenic disorders, Schnitzler's syndrome, Adult onset Still's disease, VEXAS syndrome, and autoinflammatory complications associated with myelodysplastic syndrome.

Neutrophilic dermatoses

Neutrophilic dermatoses (ND) are a group of inflammatory skin conditions characterized by a neutrophilic infiltrate on histopathology with no evidence of infection. ND are classified based upon the localization of neutrophils within the skin and clinical features. Recent findings suggest that ND are due to two main mechanisms: i) a polyclonal hereditary activation of the innate immune system (polygenic or monogenic); or ii) a clonal somatic activation of myeloid cells such as encountered in myelodysplastic syndrome or VEXAS syndrome. ND belong to internal medicine as a great number of patients with ND suffer from an underlying condition (such as hematological malignancy, inflammatory bowel disease, auto-immune and auto-inflammatory diseases). ND are diagnoses of exclusion and physicians should always consider differential diagnoses, particularly skin infections. Here, we review the pathophysiology and classification of the main ND (i.e., subcorneal pustular dermatosis (Sneddon-Wilkinson Disease) and Intercellular IgA dermatoses, aseptic pustulosis of the folds, Sweet syndrome, neutrophilic eccrine hidradenitis, pyoderma gangrenosum, erythema elevatum diutinum, neutrophilic urticarial dermatosis and neutrophilic panniculitis), their clinical and histopathological features, and we highlight the investigations that are useful to identify ND-associated diseases and to exclude the differential diagnoses.

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.

Monoclonal gammopathy of clinical significance: what the rheumatologist needs to know

Monoclonal proteins can provide important information on the diagnosis of several non-malignant systemic inflammatory disorders. At low concentration, they most commonly represent monoclonal gammopathy of undetermined significance (MGUS), whereas high concentrations often signify plasma cell myeloma or B-cell lymphoma. However, several rare inflammatory conditions associated with variable concentrations of monoclonal proteins, systemic symptoms, and organ dysfunction also exist. These conditions are termed monoclonal gammopathies of clinical significance (MGCS). Patients with MGCS might present to rheumatologists with undiagnosed systemic inflammatory disorders and the monoclonal protein provides an important, underappreciated clue for diagnosis. In this Review, we provide an approach to distinguishing MGCS from MGUS and lymphoid neoplasms, focusing on four rare MGCS that rheumatologists must recognise: scleromyxedema, Schnitzler's syndrome, idiopathic systemic capillary leak syndrome (also known as Clarkson's disease), and telangiectasias, elevated erythropoietin and erythrocytosis, monoclonal gammopathy, perinephric fluid collections, and intrapulmonary shunting (known as TEMPI) syndrome.

Cutaneous manifestations of monoclonal gammopathy

Monoclonal gammopathy associated with dermatological manifestations are a well-recognized complication. These skin disorders can be associated with infiltration and proliferation of a malignant plasma cells or by a deposition of the monoclonal immunoglobulin in a nonmalignant monoclonal gammopathy. These disorders include POEMS syndrome, light chain amyloidosis, Schnitzler syndrome, scleromyxedema and TEMPI syndrome. This article provides a review of clinical manifestations, diagnostics criteria, natural evolution, pathogenesis, and treatment of these cutaneous manifestations.

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.

Genetics of somatic auto-inflammatory disorders

Systemic autoinflammatory disorders (SAIDs) encompass a heterogeneous group of monogenic disorders characterized by recurrent episodes of systemic and organ-specific inflammation. Genetic studies have facilitated the identification of Mendelian forms of SAIDs but many patients still remain without a diagnosis. Recent studies have uncovered that somatic (acquired) mutations can cause later-onset SAIDs. In this review, we will discuss the current knowledge surrounding the genetics of these acquired auto-inflammatory disorders (AAIDs), with a focus on VEXAS, NLRP3-associated AAIDs and Schnitzler's syndrome and provide suggestions for future research in this field.

Adult-onset Still's disease or systemic-onset juvenile idiopathic arthritis and spondyloarthritis: overlapping syndrome or phenotype shift?

OBJECTIVES

Systemic-onset juvenile idiopathic arthritis (SJIA) and adult-onset Still's disease (AOSD) are the same sporadic systemic auto-inflammatory disease. Spondyloarthritis (SpA) is a group of inflammatory non-autoimmune disorders. We report the observations of eight patients with SJIA/AOSD who also presented features of SpA during their disease evolution and estimate the prevalence of SpA in SJIA/AOSD.

METHODS

This was a retrospective national survey of the departments of paediatric and adult rheumatology and internal medicine. To be included, SJIA patients had to fulfil the ILAR criteria, AOSD patients the Yamaguchi or Fautrel criteria, and all patients the ASAS classification criteria for axial or peripheral SpA, ESSG criteria for spondyloarthropathy or CASPAR criteria for psoriatic arthritis. The data were collected with a standardized form.

RESULTS

Eight patients (five adults) were identified in one paediatric and two adult departments. In all but one patient, SpA manifestations occurred several years after SJIA/AOSD onset (mean delay 6.2 ± 3.8 years). Two patients had peripheral and three axial SpA, and four later exhibited psoriatic arthritis and one SAPHO syndrome. The prevalence of SpA in an adult cohort of 76 patients with AOSD was 6.58% (95% CI [2.17-14.69]), greater than the prevalence of SpA in the French general population (0.3%, 95%CI [0.17-0.46]). The prevalence of SpA in an SJIA cohort of 30 patients was 10% (95%CI [2.11-26.53]), more than that reported in the general population of industrialized countries, estimated at 0.016% to 0.15%.

CONCLUSION

Whilst the temporal disassociation between SpA and AOSD in most cases might suggest a coincidental finding, our work raises the possibility of an SpA AOSD spectrum overlap that needs further study.

Cutaneous manifestations of lupus erythematosus: A practical clinicopathologic review for pathologists

Accurate diagnosis of connective tissue diseases is often challenging and relies on careful correlation between clinical and histopathologic features, direct immunofluorescence studies, and laboratory workup. Lupus erythematosus (LE) is a prototype of connective tissue disease with a variety of cutaneous and systemic manifestations. Microscopically, cutaneous LE is classically characterized by an interface dermatitis, although other histopathologic patterns also exist depending on the clinical presentation, location, and chronicity of the skin lesions. In this article, we review the clinical, serologic, histopathologic, and direct immunofluorescence findings in LE-specific and LE-nonspecific skin lesions, with an emphasis on lesser known variants, newly described features, and helpful ancillary studies. This review will guide general pathologists and dermatopathologists in accurately diagnosing and subclassifying cutaneous LE.

Clinical Phenotypes of Adult-Onset Still's Disease: New Insights from Pathophysiology and Literature Findings

Adult-onset Still's disease (AOSD) is a non-familial, polygenic systemic autoinflammatory disorder. It is traditionally characterized by four cardinal manifestations-spiking fever, an evanescent salmon-pink maculopapular rash, arthralgia or arthritis and a white-blood-cell count (WBC) ≥ 10,000/mm³, mainly neutrophilic polymorphonuclear cells (PMNs)-but many other manifestations and complications can be associated, making clinical expression very heterogeneous and diagnosis sometimes difficult. The AOSD course can be diverse and is currently impossible to predict. Several clinical phenotypes have been described, either on the basis of the evolution of symptoms over time (monocyclic, polycyclic and chronic evolution) or according to dominant clinical evolution (systemic and arthritis subtypes). However, these patterns are mainly based on case series and not on robust epidemiological studies. Furthermore, they have mainly been established a long time ago, before the era of the biological treatments. Thus, based on our personal experience and on recent advances in the understanding of disease pathogenesis, it appears interesting to reshuffle AOSD phenotypes, emphasizing the continuum between AOSD profiles and other systemic autoinflammatory disorders, eventually proposing a research agenda.

Approach to Children with Hives

Urticaria (or hives) is a pruritic and erythematous skin rash. Angioedema commonly occurs with urticaria. The term "chronic urticaria" is used when hives are present for more than 6 weeks. Acute urticaria is common in children, whereas chronic urticaria is rare. Causes of urticaria can be identified in many cases of acute urticaria with a thorough medical history. Laboratory evaluation may be needed to confirm the etiology of acute urticaria. Chronic urticaria is often idiopathic. Clinicians should avoid universal allergy testing for food allergens or aeroallergens in chronic urticaria as it usually does not help in identifying the cause, can lead to false-positive results, and unnecessary avoidance of allergens or foods. Urticarial vasculitis should be considered for lesions that are painful, present for more than 48 hours, leave scars/hyperpigmentation, or present with systemic symptoms such as fever, weight loss, and arthritis. Skin biopsy should be considered for suspected urticarial vasculitis. [Pediatr Ann. 2021(5):e191-e197.].

Autoinflammatory syndromes

Autoinflammatory syndromes are a steadily growing group of inflammatory diseases caused by abnormal regulations of the innate immune system. The clinical presentation is multifaceted, but recurrent fever, skin involvement, joint inflammation and other systemic symptoms of inflammation are characteristic. In contrast to classic autoimmune diseases, autoantibodies or specific T cells are not involved in the pathogenesis. In fact, innate immunity plays the most important role in autoinflammation. While activation of the innate immune system is usually self-limiting in healthy individuals, mutations and dysregulation can lead to chronic and excessive activation of innate immune responses and to the development of autoinflammatory diseases.

Non-bullous neutrophilic lupus erythematosus-Muted bullous disease?

Non-bullous neutrophilic lupus erythematosus is a rare form of cutaneous lupus erythematosus (LE). We hereby present a case of 24-year-old female, known case of discoid LE (DLE) with negative ANA stabilized on hydroxychloroquine for 2 years. She reported new occurrence of erythematous, mildly pruritic, papular lesions and painful mucosal ulceration. The ANA became strongly positive by ELISA and urine showed proteinuria. A provisional diagnosis of Rowell syndrome was made, skin biopsy was taken, and patient started on steroids. Histopathology showed interface vacuolar change and many neutrophils in the dermis with leukocytoclasia without any bulla formation. The skin lesions responded promptly to addition of dapsone following biopsy report. We conclude that the presence of neutrophils associated with interface pathology on biopsy represents a muted form of bullous LE, especially in patients on immunosuppression. This case highlights the importance of histopathologic examination in the evaluation of any new skin lesions in a patient of lupus on therapy.

Lupus erythematosus: Significance of dermatologic findings

Herein, the different skin manifestations in patients with lupus erythematosus are reviewed, and their diagnostic, pathogenic and prognostic relevance are discussed, as well as their impact on therapeutic choices. The so-called specific lesions of LE result from an autoimmune pathomechanism and they allow diagnosis of LE by simple clinicopathological correlation since the findings are characteristic. They include the classic acute, subacute and chronic variants, characterised microscopically by interface dermatitis; the dermal variants of lupus, such as tumid lupus, displaying dermal perivascular lymphocytic infiltrate with mucin deposition under the microscope, and lupus profundus, in which lymphocytic lobular panniculitis progressing to hyaline fibrosis is found. Antimalarials are the treatment of choice for patients with specific LE lesions. The presence of some dermatological signs is the result of thrombotic vasculopathy. Their recognition allows the identification of lupus patients at increased cardiovascular risk and with a worse overall prognosis. Those signs include reticulated erythema on the tip of the toes, splinter hemorrhages, atrophie blanche, pseudo-Degos lesions, racemosa-type livedo, anetoderma, ulceration and necrosis. Those clinical manifestations, often subtle, must be recognised, and if present, patients should be treated with antiplatelet drugs. Finally, neutrophilic cutaneous lupus erythematosus includes a few entities that suggest that autoinflammatory mechanisms might play a key role in certain lupus manifestations. Among those entities, it is very important to diagnose neutrophilic urticarial dermatosis, which can mimic a classic lupus flare, because it is characterised by rash with joint pain, but immunosuppressants are not helpful. Dapsone is the treatment of choice.

Schnitzler Syndrome: the paradigm of an acquired adult-onset auto-inflammatory disease

Schnitzler Syndrome is a rare acquired auto-inflammatory syndrome defined by an urticarial eruption and a monoclonal gammopathy, mainly of the IgM kappa isotype. It shares many clinical and biological features with other autoinflammatory disorders such as NLRP3-auto-inflammatory disorders (NLRP3-AID, formerly cryopyrin associated periodic syndromes or CAPS) or adult-onset Still disease (AOSD). Hence, recurrent fever, urticarial rash with a neutrophilic infiltrate on skin biopsy (i.e. neutrophilic urticarial dermatosis or NUD) and a significant elevation of blood inflammation markers are commonly found in Schnitzler Syndrome as well as in NLRP3-AID or AOSD. IL-1ß plays a crucial role in the pathogenesis and explains the clinical symptoms of Schnitzler Syndrome. This is emphasized by the spectacular effectiveness of IL-1 blocking therapies, especially anakinra. IL-1 blocking therapies are efficient on the inflammation-linked symptoms but not on the monoclonal component. The evolution is chronic and about 15-20% of patients may develop lymphoproliferative disease, in particular Waldenström disease, a proportion similar to patients with IgM monoclonal gammopathy of undetermined significance, and more rarely AA-amyloidosis.

Skin Biopsy in Chronic Urticaria: When and Where and What to Look for?

Chronic urticaria is a relatively common condition in dermatology and is usually diagnosed on clinical grounds. Skin biopsy, however, may be indicated in certain cases to confirm diagnosis and rule out other conditions that can cause hive-like rashes. We review histopathologic findings seen in both chronic urticaria and other entities in the differential diagnosis. We then propose an algorithm of indications for skin biopsy in patients with hive-like rashes and suggest possible diagnoses based on the histopathologic findings.

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.

Neutrophilic dermatoses with unusual and atypical presentations

Neutrophilic dermatoses (NDs) are a group of reactive, noninfectious autoinflammatory diseases characterized by (1) infiltration of the epidermis, dermis, and or/hypodermis by neutrophils; (2) their association with distinct diseases (eg, hematologic malignancy and chronic inflammatory diseases); (3) potential extracutaneous involvement; and (4) response to anti-inflammatory drugs, such as corticosteroids, dapsone, colchicine, and novel biologic therapies, such as the anti-interleukin-1 blockade. Although distinct NDs have been described, transitional forms with overlapping features are often identified. These justify a simplified classification of NDs with three major forms: superficial (epidermal or pustular) NDs, dermal (en plaques) NDs, and deep NDs. We review selected or novel variants of NDs, including subcorneal pustular dermatosis, the group of immunoglobulin A neutrophilic dermatoses, amicrobial pustular dermatosis of the folds, and neutrophilic urticarial dermatosis, as well as atypical forms of Sweet syndrome and pyoderma gangrenosum closely mimicking severe infectious diseases. Knowledge of these variants is essential for proper diagnosis, adequate management, and avoidance of a dangerous escalation of therapy, such as unnecessary immunosuppression or extensive surgery.

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.

[Neutrophilic and pustular dermatoses : New autoinflammatory diseases and syndromes]

This article reviews noninfectious inflammatory dermatoses with mainly neutrophilic infiltrates and the formation of pustules. The infiltrate containing neutrophils may either be mild as in urticaria or very dense, even with leukocytoclasia, as in Sweet syndrome or pyoderma gangrenosum. Neutrophilic infiltrates and pustular eruptions are caused by different noninfectious immunomechanisms. For some of them, mutations have been found (e.g. NLRC4 mutation in cryopyrin-associated periodic syndromes (CAPS) leading to activation of the inflammasome; IL36RN mutation in pustular psoriasis resulting in uncontrolled IL36 signaling). Neutrophilic dermatoses are of high interest, as they may be the cause of underlying benign or malignant conditions. In recent years, efficient targeted therapies have been developed.