Sweet syndrome induced by FLT3 inhibitors: case report and literature review.

BACKGROUND: Acute febrile neutrophilic dermatosis, also commonly referred to as Sweet syndrome, is often associated with tumors, infections, immune disorders and medications. FLT3 inhibitor-induced Sweet syndrome is a rare complication. METHODS AND RESULTS: We report a patient with relapsed and refractory acute monocytic leukemia harboring high-frequency FLT3-ITD and DNMT3a mutations. The FLT3 inhibitor gilteritinib was administered for reinduction therapy after failure of chemotherapy with a combination of venetoclax, decitabine, aclarubicin, cytarabine and granulocyte colony-stimulating factor. The leukemia patient achieved remission after 1 month of treatment. However, Sweet syndrome induced by gilteritinib, which was confirmed by skin biopsy, developed during induction therapy. Similar cases of Sweet syndrome following FLT3 inhibitor therapy for acute myeloid leukemia were reviewed. CONCLUSION: Attention should be given to this rare complication when FLT3 inhibitors are used for acute myeloid leukemia therapy, and appropriate treatments need to be administered in a timely manner.

Case Report: Type 2 Leprosy Reaction Mimicking Sweet Syndrome: A Case Report and Literature Review.

Type 2 leprosy reaction is a type of acute inflammation that predominantly affects borderline lepromatous leprosy and lepromatous leprosy patients and occurs before, during, or after therapy. The atypical variant, which resembles Sweet syndrome, could easily lead to misdiagnosis. Here, we report a case of a 52-year-old man who presented with type 2 leprosy reaction that mimicked Sweet syndrome. In addition, we review published cases and summarize their features to raise awareness of this atypical variant to enable improved diagnosis and management.

Mercaptopurine-induced Sweet's syndrome.

Sweet's syndrome is an acute febrile neutrophilic dermatosis. Drug-induced Sweet's syndrome typically occurs soon after drug administration, with rapid resolution of symptoms with cessation of the offending agent. We report a man in his early 40s who presented with fever and widespread erythematous rash on a background of recently diagnosed mild stricturing ileal Crohn's disease. He was commenced on 6-mercaptopurine 12 days before presentation. Skin biopsy demonstrated diffuse infiltration of neutrophils in the upper dermis, dermal oedema, eosinophils and fibrin deposition. Symptoms rapidly improved with cessation of 6-mercaptopurine without requiring systemic corticosteroids.

Overview of Neutrophilic Biology, Pathophysiology, and Classification of Neutrophilic Dermatoses.

Neutrophilic dermatoses are a group of inflammatory skin conditions characterized by a neutrophilic infiltrate on histopathology with no evidence of infection. These conditions present with a wide range of clinical manifestations, including pustules, bullae, abscesses, papules, nodules, plaques, and ulcers. The classification of neutrophilic dermatoses is based on the localization of neutrophils in the skin. The pathogenic mechanisms of neutrophilic dermatoses involve autoinflammation, neutrophilic dysfunction, clonal somatic mutation and differentiation of the myeloid precursors as encountered in myeloid neoplasm.

Sweet Syndrome and Neutrophilic Dermatosis of the Dorsal Hands.

Sweet syndrome is a rare cutaneous condition with a broad clinical differential diagnosis. It can be classified into 3 subtypes: classic, malignancy-associated, and drug-induced. There are numerous associated disorders and provoking medications. Uncommonly, it can present as a multiorgan disease and cause significant morbidity. Systemic corticosteroids are the gold standard of treatment and yield rapid improvements in both lesions and symptoms. Nonsteroidal therapies may be effective alternatives, although high-quality comparative data are lacking. Some treatments for Sweet syndrome have paradoxically been implicated in the induction of disease.

From Histiocytoid Sweet Syndrome to Myelodysplasia Cutis: History and Perspectives.

In 2005, a new histologic variant of Sweet syndrome (SS) has been described and termed histiocytoid SS (HSS). Clinically, patients had a typical SS, but on skin biopsy, the infiltrates were composed of immature nonblast myeloid cells. Nearly 50% of patients with HSS have myelodysplastic syndrome (MDS). HSS may be the first manifestation leading to the diagnosis of MDS. In 2015, a new category of myeloid dermatosis has been proposed, called myelodysplasia cutis, describing the specific skin infiltration by myelodysplastic cells in patients with MDS.

Pediatric Neutrophilic Dermatoses.

The term neutrophilic dermatosis encompasses a heterogeneous group of diseases, often associated with an underlying internal noninfectious disease, with an overlapping histopathologic background characterized by perivascular and diffuse neutrophilic infiltrates in one or more layers of the skin; extracutaneous neutrophilic infiltrates may be associated. Neutrophilic dermatoses are not frequent in children and, when they appear in this age group, represent a diagnostic and therapeutic challenge. Apart from the classic neutrophilic dermatoses such as pyoderma gangrenosum, Sweet syndrome, and Behçet disease, a neutrophilic dermatosis can be the presentation of rare genetic diseases of the innate immune system, such as autoinflammatory diseases.

Sweet syndrome following the ChAdOx1-S vaccine.

We report a case of vaccine-induced Sweet syndrome in a female patient in her 50s presenting with fevers and a scattered red patchy rash on the lower limbs. Seven days prior, she had received the first dose of AstraZeneca ChAdOx1-S vaccine. A skin biopsy confirmed Sweet syndrome. She did not respond to high doses of prednisolone and required methotrexate therapy to induce remission. This is one of the first reports of Sweet syndrome caused by the ChAdOx1-S vaccine and provides further evidence for vaccine-induced dermatosis. This case demonstrates that methotrexate can induce remission in cases of Sweet syndrome resistant to corticosteroids. This report also describes an approach to the differential diagnosis of patients presenting with a rash, fever and malaise.

Azathioprine hypersensitivity: A Sweet-like syndrome.

INTRODUCTION: Azathioprine hypersensitivity can occasionally present as Sweet-like syndrome, a dose-independent side effect characterized by the unanticipated onset of macules, papules, and pustules. CASE PRESENTATION: A 35-year-old woman with systemic lupus erythematosus presented with complaints of generalized maculopapular rash, facial swelling, and bilateral lower extremity edema with a duration of 4 days and a 2-day history of constitutional symptoms within 2 weeks of the beginning of azathioprine therapy to treat existing lupus nephritis (class 2/3). DISCUSSION: Patients who experience azathioprine hypersensitivity syndrome can present with erythema nodosum, small-vessel vasculitis, acute generalized exanthematous pustulosis, Sweet syndrome, and nonspecific dermatosis. The following signs and symptoms are used as criteria to diagnose drug-induced Sweet syndrome: (a) abrupt onset of painful erythematous plaques, (b) histopathological evidence of dense neutrophilic infiltrate without evidence of leukocytoclastic vasculitis, (c) temperature higher than 39.7°C, (d) temporal relationship between drug ingestion and clinical presentation, and (e) temporal resolution of lesions after drug withdrawal. Our patient met three out of five criteria and was diagnosed with Sweet-like syndrome. CONCLUSION: Our case highlights the uncommonly presented azathioprine-induced Sweet-like syndrome that occurs abruptly after the commencement of the offending drug. This diagnosis can be established through basic laboratory workup and skin biopsy findings.

A diagnostic challenge-First case of chronic lymphatic leukemia-associated necrotizing sweet syndrome.

Sweet syndrome, also known as acute febrile neutrophilic dermatosis, is a rare disorder typically characterized by the clinical triad including a sudden onset of fever, painful skin lesions, and neutrophilia. The histopathological findings are a dense neutrophilic infiltrate and oedema of the dermis and epidermis without evidence of a vasculitis. Besides treatment of the underlying cause, sweet syndrome is typically treated with high-dose corticosteroids leading to a relapse-free response in 70% of patients. However, if left unrecognized or untreated, the condition may lead to serious complications. Here, we report on the case of a 38-year-old patient in whom, under the assumption of the presence of necrotizing fasciitis, exarticulation of the right arm was performed. In the absence of pathogen detection and insufficient response to anti-infective therapies, the diagnosis of a sweet syndrome was assumed and, later, confirmed by an excellent response to high-dose administration of systematic glucocorticoids. The case emphasizes the need to be aware of this rare syndrome, which can be easily misdiagnosed due to its close resemblance to infection and stresses the need of further research to define distinct diagnostic tools.

Sweet Syndrome: Clinical Presentation, Malignancy Association, Autoinflammatory Disorders and Treatment Response in a Cohort of 93 Patients with Long-term Follow-up.

Sweet syndrome is a neutrophilic dermatosis associated with multiple disorders. This retrospective case-series study of patients with Sweet syndrome in a tertiary hospital in Spain from 2001 to 2021, explores clinicopathological characteristics of Sweet syndrome and variables associated with malignancy, presence of autoinflammatory disorders and differences between histological subtypes. A total of 93 patients were identified: 30% idiopathic, 34% malignancy-associated, 29% reactive to infections or drug-associated, and 6% with an autoimmune/inflammatory condition. Acute myeloid leukaemia was the most common malignancy (16/93) followed by myelodysplastic syndrome (7/93). Patients with acute myeloid leukaemia presented isolated flares, marked cytopaenia and rapid response to treatment, whereas myelodysplastic syndrome followed a chronic-recurrent course. The most frequent associated medications and inflammatory  disorders were filgrastim and hydroxyurea (n = 2);  and inflammatory bowel disease (n = 4). In addition, 3 patients were diagnosed with VEXAS syndrome. Male sex (p = 0.006), fever (p = 0.034), increased erythrocyte sedimentation rate (p < 0.001), anaemia (p < 0.001), and thrombocytopaenia (p < 0.001) were associated with malignancy. Histologically, patients were classified as classic (60%), histiocytoid (22.5%) or subcutaneous (15%), with pain (p = 0.011) and nodules (p < 0.001) being associated with subcutaneous-Sweet syndrome. Sweet syndrome in the context of cytopaenia should alert the presence of malignancy. An  acquired autoinflammatory condition should be explored  in relapsing Sweet syndrome with myelodysplastic syndrome. A minimum follow-up of 6 months is recommended.

VEXAS-Syndrome, a newly described autoinflammatory systemic disease with dermatologic manifestations.

VEXAS syndrome is a recently identified autoinflammatory systemic disease caused by an acquired somatic mutation of the X-linked UBA1 gene, the key enzyme of the first step of ubiquitylation. The acronym VEXAS stands for the characteristics Vacuoles, E1 enzyme, X-linked, autoinflammatory and somatic. The disease occurs in advanced adulthood preferentially in men and is characterized by hematological, rheumatological and dermatological symptoms. The latter include neutrophil-rich lesions reminiscent of Sweet's syndrome, erythema nodosum- and panniculitis-like skin manifestations and recurrent polychondritis of the nose and auricles. The presence of cytoplasmic vacuoles in myeloid and erythroid precursors in the bone marrow is characteristic. In up to half of the cases, VEXAS syndrome is associated with myelodysplastic syndrome. Dermatologists should be familiar with the clinical picture, as skin symptoms are often the first indicator of the disease. Molecular diagnostics are essential for confirming the diagnosis and risk stratification of affected patients. In this minireview we provide an overview of the pathophysiology, diagnosis and therapy of VEXAS syndrome and illustrate its clinical picture with two own cases.

A case of neonatal sweet syndrome associated with mevalonate kinase deficiency.

BACKGROUND: Sweet syndrome (SS), also known as acute febrile neutrophilic dermatosis, is an immunologic syndrome characterized by widespread neutrophilic infiltration. Histiocytoid Sweet syndrome (H-SS) is a histopathologic variant of SS. While SS most commonly occurs in adults, this case report discusses an infant patient who presented with H-SS. CASE PRESENTATION: Through a multidisciplinary approach, this patient was also found to have very early onset inflammatory bowel disease (VEO-IBD) and Mevalonate kinase-associated disease (MKAD). While prior case studies have characterized an association between VEO-IBD and MKAD, there is no literature describing the association of all three diagnoses this case: H-SS, VEO-IBD and MKAD. Initiation of canakinumab in this patient resulted in successful control of the disease. CONCLUSIONS: This case highlights the importance of a multidisciplinary approach to rare diagnoses, and collaboration during cases with significant diagnostic uncertainty.

Periorbital Necrotizing Sweet's Syndrome: A Case Report.

Sweet's syndrome (acute febrile neutrophilic dermatosis) is an uncommon inflammatory condition most often associated with painful skin lesions of the head, neck, and upper extremities. To the authors' knowledge, this case report is the only published record of the necrotizing clinical variant of Sweet's syndrome in the periorbital space. This case follows a 91-year-old female who presented with generalized cutaneous eruptions of tender erythematous plaques, including a necrotic plaque of the left upper eyelid, and pancytopenia. A biopsy of an inner thigh lesion was consistent with Sweet's syndrome. Initially diagnosed with preseptal cellulitis, the patient experienced marked clinical improvement with corticosteroids. This, coupled with the histopathologic findings of her thigh biopsy and the absence of eyelid margins, led to the diagnosis of periorbital necrotizing Sweet's syndrome. Although cases of Sweet's syndrome in the periorbital region are rare, these diagnoses should not be overlooked and may be critical to patient care.

Clinical characteristics, diagnosis and management of Sweet syndrome induced by azathioprine.

Sweet syndrome is a rare complication of azathioprine treatment with unelucidated clinical features. The purpose of this study was to investigate the clinical characteristics of azathioprine-induced Sweet syndrome (AISS) and provide a reference for diagnosis, treatment and prognosis. We collected relevant case reports of AISS by searching Chinese and English databases from 1960 to December 31, 2022, extracted the data and carried out a retrospective analysis. The median age of the 44 patients was 50 (range 9-89) years, and they included 32 males (72.7%). Fever (86.4%) and arthralgia (31.8%) were the most common clinical symptoms. The skin lesions were mainly pustules (54.5%), papules (40.9%), plaques (40.9%) and nodules (31.8%), which were mainly distributed on the extremities (54.5%), face (38.6%) and hands (36.4%). Laboratory examination revealed neutropenia (65.9%) as well as elevated C-reactive protein (63.6%) and erythrocyte sedimentation (40.9%) rates. Histopathology of the lesioned skin showed neutrophil infiltration (93.2%) and dermal edema (38.6%). Symptom relief was achieved at a median time of 7 days (range 2-28 days) after azathioprine discontinuation in all patients. Nine patients (20.5%) had skin lesions that recurred within 24 h after taking azathioprine again. Clinicians and pharmacists should grasp the regularity and characteristics of AISS and should not recommend the readministration of azathioprine, to avoid the recurrence of Sweet syndrome.