Novel Therapeutic Approaches and Targets for the Treatment of Neutrophilic Dermatoses, Management of Patients with Neutrophilic Dermatoses and Future Directions in the Era of Biologic Treatment.

Neutrophilic dermatoses are a heterogeneous group of inflammatory skin disorders characterized by the presence of a sterile, predominantly neutrophilic infiltrate on histopathology. Universally accepted and validated guidelines for the management of neutrophilic dermatoses do not exist, also given the paucity of randomized controlled study and high-quality data. However, the literature on the effective use of biologic therapies is rapidly expanding. This article reviews the epidemiology, clinical characteristics, histopathologic features, and management of pyoderma gangrenosum as well as Sweet's syndrome, sub-corneal pustular dermatoses and bowel-associated dermatosis arthritis syndrome. The use of biologic agents, including tumor necrosis factor α-inhibitors, anti-IL1, anti-IL-17, and IL-23 are discussed in detail.

Scarring alopecia in chronic cutaneous lupus erythematosus with neutrophils: A new scenario with therapeutic connotations.

The relationship between autoinflammatory and autoimmune conditions has been demonstrated in recent decades. Several autoimmune conditions exhibit an autoinflammatory component, which can manifest in various ways. Neutrophilic dermatosis in the context of lupus erythematosus (LE) is one example. Otherwise, neutrophils are rare in LE, except for the bullous variant and nonbullous neutrophilic LE. In this paper, we describe a case of scarring alopecia due to LE that stopped responding to a treatment that had been effective for years. The biopsy specimen demonstrated the presence of neutrophils in the inflammatory infiltrate. A treatment with dapsone was prescribed and yielded rapid improvement. This first case of scarring alopecia in the context of nonbullous neutrophilic LE emphasizes the importance of the infiltrate in determining the optimal therapeutic choice.

Efficacy of acitretin in the treatment of reactive neutrophilic dermatoses in adult-onset immunodeficiency due to interferon-gamma autoantibody.

Reactive neutrophilic dermatoses in adult-onset immunodeficiency due to interferon-γ autoantibody (AOID) are usually associated with concomitant active opportunistic infections. Data focusing on the treatment of these dermatoses with non-immunosuppressive drugs are still lacking. The aim of this study was to assess the efficacy and safety of acitretin treatment of reactive neutrophilic dermatoses in AOID. We conducted a retrospective review of all patients with AOID who had reactive neutrophilic dermatoses and had been treated with acitretin from January 2008 to December 2018. In total, 23 patients had been diagnosed with AOID, with 27 episodes of reactive neutrophilic dermatoses (20 episodes of Sweet syndrome and seven episodes of generalized pustular eruption) and treated with acitretin. The median effective dose of acitretin was 10 mg/day. The mean initial response was 5.6 ± 2.3 days. The rash had almost or completely cleared within 2 weeks in 70.4% of patients. One case had developed a reversible acitretin-induced liver injury with hepatocellular pattern. The median total duration of treatment was 3 months. In conclusion, this study demonstrates the potential role of acitretin as one of the treatments of choice for reactive neutrophilic dermatoses in AOID, attributable to its favorable response and good tolerability.

Superficial and Deep Cutaneous Involvement by RAS-Associated Autoimmunne Leukoproliferative Disease (RALD Cutis): A Histologic Mimicker of Histiocytoid Sweet Syndrome.

RAS-associated autoimmune leukoproliferative disease (RALD) is a recently described noninfectious and nonmalignant clinical syndrome characterized by autoimmune disorders, massive splenomegaly, modest lymphadenopathy, and monocytosis. On the molecular level, RALD is defined by somatic mutations of either NRAS or KRAS gene in a subset of hematopoietic cells. To date, there is a dearth of well-documented histopathologic description of cutaneous involvement by RALD in the literature. In the current case report, a 43-year-old female patient with a history of RALD presented with clinical pictures of sepsis and an erythematous rash in the left lower extremity. Histologic examination revealed a dense perivascular and interstitial infiltrate of immature myeloid cells admixed with scattered neutrophils involving the dermis and subcutaneous adipose tissue, imparting a panniculitis-like histologic pictures. There was a strong angiocentric propensity of the immature hematopoietic cells as well as extensive extravasation of red blood cells, even in the subcutaneous adipose tissue. Immunohistochemically, the immature hematopoietic cells were positive for CD43, CD4, and CD68, but negative for CD34, CD117, and myeloperoxidase. Overall, the histologic and cytologic findings were highly reminiscent of histiocytoid Sweet syndrome. Review of the English literature revealed cutaneous involvements by RALD only in patients with KRAS mutation compared with none of its NRAS counterparts. However, larger clinicopathologic studies on cutaneous involvement by RALD are warranted. The term "RALD cutis" with its histologic and molecular features is suggested to serve as a potential groundwork for future studies of this rare phenomenon.

A case of neutrophilic dermatosis with MEFV gene variant and abnormal activation of peripheral blood monocytes: a case report.

A healthy 32-year-old man had a fever and elevated levels of white blood cells (WBC) and C-reactive protein (CRP). In addition, he presented with a skin rash on his forehead, around the neck, and from the anterior chest to the abdomen. His laboratory findings showed elevated levels of hepatic enzyme, CRP, and ferritin; therefore, he was suspected to have adult-onset Still's disease (AOSD) and referred to our department. We ruled out hematological malignancy and established diagnosis of AOSD according to Yamaguchi's criteria and treated with 20 mg/day prednisolone. His clinical condition did not improve, therefore, we increased the dosage of prednisolone to 40 mg/day; however, his rash gradually expanded with papules and plaques. A cervical skin biopsy revealed neutrophil dermatosis and analysis of the MEFV gene revealed a heterozygous variant in exon 2 (E148Q). We found an elevated percentage of CD86+CD14+CD16- classical monocytes in the peripheral blood using flow cytometry. We added oral potassium iodide as a treatment for neutrophil dermatosis. Despite this treatment, his eruption and fever did not subside, therefore, we changed potassium iodide to colchicine, this improved his clinical condition. This case suggests the importance of autoinflammation-related gene abnormalities and macrophage activation in the pathogenesis of neutrophil dermatosis.

Insights Into the Pathogenesis of Sweet's Syndrome.

Sweet's syndrome, also known as Acute Febrile Neutrophilic Dermatosis, is a rare inflammatory condition. It is considered to be the prototype disease of neutrophilic dermatoses, and presents with acute onset dermal neutrophilic lesions, leukocytosis, and pyrexia. Several variants have been described both clinically and histopathologically. Classifications include classic Sweet's syndrome, malignancy associated, and drug induced. The cellular and molecular mechanisms involved in Sweet's syndrome have been difficult to elucidate due to the large variety of conditions leading to a common clinical presentation. The exact pathogenesis of Sweet's syndrome is unclear; however, new discoveries have shed light on the role of inflammatory signaling, disease induction, and relationship with malignancy. These findings include an improved understanding of inflammasome activation, malignant transformation into dermal infiltrating neutrophils, and genetic contributions. Continued investigations into effective treatments and targeted therapy will benefit patients and improve our molecular understanding of inflammatory diseases, including Sweet's syndrome.

Skin Manifestations in Patients with Adult-onset Immunodeficiency due to Anti-interferon-gamma Autoantibody: A Relationship with Systemic Infections.

Adult-onset immunodeficiency due to anti-interferon-γ autoantibody is an emerging acquired immunodeficiency with frequent skin manifestations. A retrospective chart review was conducted and identified 41 patients with the syndrome. Skin involvement was detected in 33 (80%) patients, 15 (45%) with infective skin diseases and 27 (82%) with reactive skin disorders. Reactive lesions were mostly neutrophilic dermatoses, e.g. Sweet syndrome. Of note, the presence of neutrophilic dermatoses was highly associated with infections of other sites. An adjusted odds ratio for the existence of infections in patients with neutrophilic dermatoses was 14.79 (95% CI: 5.13, 42.70; p < 0.001). Moreover, neutrophilic dermatoses were significantly correlated with opportunistic infections observed in those with defects in cell-mediated immunity including non-tuberculous mycobacterium and disseminated fungal infection. The odds ratio for opportunistic infections in the presence of neutrophilic dermatoses was 12.35 (95% CI: 5.00, 30.55; p <0.001). Thus, the presence of neutrophilic dermatoses in patients with the syndrome can signal opportunistic infections that warrant physician attention.

ASK1/2 signaling promotes inflammation in a mouse model of neutrophilic dermatosis.

Mice homozygous for the Tyr208Asn amino acid substitution in the carboxy terminus of Src homology region 2 (SH2) domain-containing phosphatase 1 (SHP-1) (referred to as Ptpn6spin mice) spontaneously develop a severe inflammatory disease resembling neutrophilic dermatosis in humans. Disease in Ptpn6spin mice is characterized by persistent footpad swelling and suppurative inflammation. Recently, in addition to IL-1α and IL-1R signaling, we demonstrated a pivotal role for several kinases such as SYK, RIPK1, and TAK1 in promoting inflammatory disease in Ptpn6spin mice. In order to identify new kinases involved in SHP-1-mediated inflammation, we took a genetic approach and discovered apoptosis signal-regulating kinases 1 and 2 (ASK1 and ASK2) as novel kinases regulating Ptpn6-mediated footpad inflammation. Double deletion of ASK1 and ASK2 abrogated cutaneous inflammatory disease in Ptpn6spin mice. This double deletion further rescued the splenomegaly and lymphomegaly caused by excessive neutrophil infiltration in Ptpn6spin mice. Mechanistically, ASK regulates Ptpn6spin-mediated disease by controlling proinflammatory signaling in the neutrophils. Collectively, the present study identifies SHP-1 and ASK signaling crosstalk as a critical regulator of IL-1α-driven inflammation and opens future avenues for finding novel drug targets to treat neutrophilic dermatosis in humans.

A Comprehensive Review of Neutrophilic Diseases.

Neutrophilic dermatoses are a group of conditions characterized by the accumulation of neutrophils in the skin and clinically presenting with polymorphic cutaneous lesions, including pustules, bullae, abscesses, papules, nodules, plaques and ulcers. In these disorders, the possible involvement of almost any organ system has lead to coin the term 'neutrophilic diseases'. Neutrophilic diseases have close clinicopathological similarities with the autoinflammatory diseases, which present with recurrent episodes of inflammation in the affected organs in the absence of infection, allergy and frank autoimmunity. Neutrophilic diseases may be subdivided into three main groups: (1) deep or hypodermal forms whose paradigm is pyoderma gangrenosum, (2) plaque-type or dermal forms whose prototype is Sweet's syndrome and (3) superficial or epidermal forms among which amicrobial pustulosis of the folds may be considered the model. A forth subset of epidermal/dermal/hypodermal forms has been recently added to the classification of neutrophilic diseases due to the emerging role of the syndromic pyoderma gangrenosum variants, whose pathogenesis has shown a relevant autoinflammatory component. An increasing body of evidence supports the role of pro-inflammatory cytokines like interleukin (IL)-1-beta, IL-17 and tumour necrosis factor (TNF)-alpha in the pathophysiology of neutrophilic diseases similarly to classic monogenic autoinflammatory diseases, suggesting common physiopathological mechanisms. Moreover, mutations of several genes involved in autoinflammatory diseases are likely to play a role in the pathogenesis of neutrophilic diseases, giving rise to regarding them as a spectrum of polygenic autoinflammatory conditions. In this review, we focus on clinical aspects, histopathological features and pathophysiological mechanisms of the paradigmatic forms of neutrophilic diseases, including pyoderma gangrenosum, Sweet's syndrome, amicrobial pustulosis of the folds and the main syndromic presentations of pyoderma gangrenosum. A simple approach for diagnosis and management of these disorders has also been provided.

Inflammatory Joint Disorders and Neutrophilic Dermatoses: a Comprehensive Review.

Rheumatoid arthritis and spondyloarthritis are inflammatory joint disorders with an autoimmune pathogenesis and systemic involvement. The skin is one of the most frequently affected extraarticular sites with a number of manifestations or distinct diseases, including common conditions, such as rheumatoid nodules and psoriasis, and rare diseases like neutrophilic dermatoses. The latter are clinically characterised by polymorphic lesions, including pustules, bullae, abscesses, papules, nodules, plaques and ulcers, and histologically by neutrophil-rich inflammatory infiltrates. Inflammatory joint disorders and neutrophilic dermatoses share a number of pathophysiological features related to their cytokine overexpression profile. Moreover, any organ system can be potentially involved in neutrophilic dermatoses, giving rise to the concept of neutrophilic disease. Among the extracutaneous manifestations of neutrophilic disease, joint involvement is regarded as the most common. It is not associated with erosions and disability and usually responds to treatment for skin involvement, consisting of systemic corticosteroids and, in refractory cases, immunosuppressants or biologics. Arthritis may also be the initial manifestation of rheumatoid arthritis or spondyloarthritis, which has a chronic or recurrent course and requires a continuous treatment with synthetic or biologic disease-modifying anti-rheumatic drugs. If not properly treated, they may be associated with disability and reduced quality of life. Skin lesions occurring during the course of rheumatoid arthritis and spondyloarthritis require a multidisciplinary approach envisaging the collaboration of dermatologists and rheumatologists in order to achieve early diagnosis and treatment. Several biomarkers may help the clinician in the differential diagnosis of arthritis while histology is pivotal for the correct classification of the skin disease. However, in some cases, only regular follow-up allows a definite diagnosis. In this review article, we focus on the prototypic neutrophilic dermatoses like pyoderma gangrenosum, Sweet's syndrome, hidradenitis suppurativa and their syndromic forms as well as on their articular involvement, providing a simple approach for their diagnosis and therapy.

Function and mechanism of the pyrin inflammasome.

Pyrin, encoded by the MEFV gene, is an intracellular pattern recognition receptor that assembles inflammasome complexes in response to pathogen infections. Mutations in the MEFV gene have been linked to autoinflammatory diseases such as familial Mediterranean fever (FMF) or pyrin-associated autoinflammation with neutrophilic dermatosis (PAAND). Recent insights have now revealed how pyrin is activated during infection, providing a molecular basis for the understanding of such disease-causing mutations in pyrin. Interestingly, pyrin does not directly recognize molecular patterns (pathogen- or host-derived danger molecules), but rather responds to disturbances in cytoplasmic homeostasis caused by the infection. In the case of pyrin, these perturbations, recently defined as 'homeostasis-altering molecular processes' (HAMPs), are processes leading to the inactivation of the RhoA GTPase. This review attempts to combine early observation and findings with the most recent discoveries on how pyrin detects inactivation of RhoA to shed light on the function and mechanism of pyrin activation.

Monogenic interferonopathies: Phenotypic and genotypic findings of CANDLE syndrome and its overlap with C1q deficient SLE.

OBJECTIVE: To report the clinical and genetic features of the first cases of chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperature (CANDLE) syndrome in an Arab population and to compare them with patients of C1q deficient systemic lupus erythematosus (SLE). MATERIALS AND METHODS: This is a retrospective case series of patients with CANDLE syndrome and C1q deficient SLE seen at a single tertiary hospital. Medical records were reviewed for demographic data, clinical and laboratory features, histopathology and imaging findings, and response to therapeutic intervention. Descriptive data were summarized. RESULTS: Three patients from unrelated families fulfilled the clinical manifestations of CANDLE syndrome. The disease onset was within the first 4 months of age. Two patients had uncommon features including uveitis, pulmonary involvement, aseptic meningitis and global delay. Skin biopsy showed heterogeneous findings. Genomic DNA screening was homozygous for mutation in PSMB8, (NM_004159.4:c.212C>T, p.T71M) in one patient and inconclusive for the other two patients. The comparison group was three patients with familial C1q deficient SLE from three unrelated families, who were born to consanguineous parents with at least one affected sibling. They presented with extensive mucocutaneous lesions, discoid rash and scarring alopecia. They required frequent admissions due to infections. CONCLUSION: This is the first report of CANDLE syndrome in an Arab population; our patients had heterogeneous phenotypic and genetic features with overlap manifestations with C1q deficient SLE. Both are monogenic interferonopathies. However, C1q deficient SLE had more systemic inflammatory disease.

Neutrophilic urticarial dermatosis and Sweet-like neutrophilic dermatosis: under-recognized neutrophilic dermatoses in lupus erythematosus.

Background/Objectives Neutrophilic dermatoses can be associated with autoimmune connective tissue diseases such as systemic lupus erythematosus (SLE). We analyzed clinical and histological features of neutrophilic urticarial dermatosis (NUD) and Sweet-like neutrophilic dermatosis (SLND)-the most recently delineated entities of the neutrophilic dermatoses. Methods We retrieved database medical records of patients with SLE whose skin biopsy demonstrated a neutrophilic-predominant infiltrate of the skin, and included those whose biopsies revealed findings of SLND or NUD. Results SLND skin lesions lasted longer than those of NUD and were localized to sun-exposed areas. All NUD cases resolved within one week either spontaneously or with treatment such as antihistamines, but SLND skin lesions lasted longer than one week; prednisone was used in four of these five patients. All NUD cases were found in existing SLE patients and were not associated with systemic signs of flare-up of SLE. However, 80% of SLND cases experienced flare-up of SLE; and in 60%, SLND developed concomitantly with SLE as a presenting sign. Conclusion Different clinical courses and relationships with SLE suggest that NUD and SLND have different pathogeneses for neutrophilic inflammatory reactions.

Sweet's syndrome: diagnostic criteria revisited.

The diagnosis of Sweet's syndrome (SS) is based on a set of criteria that requires the presence of two major and at least two minor criteria. In some cases, however, the diagnosis is not as straightforward due to the absence of certain criteria. The objective of the present study was to review the clinical, histopathological, and laboratory features of the current diagnostic criteria for SS, and to evaluate their validity in the cases reported in the literature as well as in 40 patients treated at our institution. Our comprehensive review of the current criteria for SS reveals that the two major criteria have been consistently present in all cases - including ours - since the first description of SS in 1964. With regard to the minor criteria, on the other hand, there has been marked variability between different studies, and many cases failed to fulfill the requirement of showing two minor criteria. In order to simplify the diagnosis, avoid misdiagnosis, and allow for prompt treatment, we propose two sets of revised diagnostic criteria for SS. The first set comprises constant clinical and histopathological features that must be present and are by themselves sufficient for the diagnosis of SS to be established. The second set includes variable features whose absence does not warrant ruling out SS.