Sweet or Not? Azathioprine-Induced Sweet Syndrome Mimicking Erythema Nodosum in a Patient With Inflammatory Bowel Disease

This case report highlights the clinical challenge and need to distinguish Sweet syndrome and erythema nodosum (EN) in a 50-year-old woman with newly initiated azathioprine for inflammatory bowel disease. While she initially presented with clinical features concerning for drug-induced Sweet syndrome, a subsequent histopathological examination confirmed early-stage EN. Both Sweet syndrome and EN share common triggers and therapeutic responses, but have distinctive clinical characteristics. Subtle histologic differences also exist in lesion distribution and depth of infiltration. This case underscores the need for accurate differentiation in patients with inflammatory bowel disease to initiate appropriate management and avoid potential complications.

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.

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.

Systematic Review: Sweet Syndrome Associated with Inflammatory Bowel Disease

BACKGROUND AND AIMS

Sweet syndrome [SS] is a dermatological condition associated with both inflammatory bowel disease [IBD] and azathioprine use. We performed a systematic review to better delineate clinical characteristics and outcomes of SS in IBD patients.

METHODS

Peer-reviewed, full-text journal publications from inception to April 2020 in English language and adult subjects with IBD were included. Skin biopsy was required as SS gold-standard diagnosis. Azathioprine-associated SS required recent azathioprine introduction or recurrence of SS after azathioprine re-challenge.

RESULTS

We included 89 publications with 95 patients [mean age of SS diagnosis: 44 years; 59% female; 20 with azathioprine-associated SS and 75 without]. SS was diagnosed prior to IBD in 5.3%, at time of IBD diagnosis in 29.5% and after diagnosis in 64.2%. In total, 91% of patients with SS had known colonic involvement and the majority [76%] had active IBD at diagnosis; 22% had additional extra-intestinal manifestations. Successful therapies for SS included corticosteroids [90.5%], anti-tumour necrosis factor [TNF]-α inhibitor therapy [14.8%] and azathioprine [11.6%]. Azathioprine-associated SS was distinct, with 85% male patients, mean age of SS diagnosis of 50 years and a lower likelihood to be prescribed corticosteroids for treatment [75% vs 94.7% of non-azathioprine-associated SS, p = 0.008]. All patients with azathioprine-associated SS improved with medication cessation and developed recurrence after re-challenge.

CONCLUSIONS

SS may precede or occur with IBD diagnosis in almost one-third of cases. Azathioprine and IBD-associated SS present and behave distinctly, especially with regard to gender, age at diagnosis and recurrence risk. Corticosteroids and TNF-α inhibitors have demonstrated efficacy in treating SS in IBD.

Azathioprine Hypersensitivity Syndrome during Treatment of Severe Interstitial Lung Disease with Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis

Azathioprine is used to treat anti-neutrophil cytoplasmic antibody- (ANCA-) associated vasculitis. Azathioprine hypersensitivity syndrome is often missed. An 81-year-old man undergoing treatment for interstitial pneumonia developed a high fever and was diagnosed with ANCA-associated vasculitis based on an elevated myeloperoxidase- (MPO-) ANCA titer and renal biopsy findings. After induction therapy, his clinical symptoms improved, but his MPO-ANCA remained elevated (>300 U·L⁻¹) and hematuria persisted. Prednisolone plus azathioprine was administered as maintenance therapy. Three exacerbations of the inflammatory response occurred during the subsequent 3 months. In each instance, we suspected opportunistic infection or a flare-up of vasculitis. The first exacerbation was treated with an increased prednisolone dose and antibiotics. At the onset of the second exacerbation, which was accompanied by systemic erythema, we stopped azathioprine and administered antibiotics. The third exacerbation, which occurred the day after restarting azathioprine, involved a fever with chills and an acute inflammatory reaction; we therefore suspected an azathioprine allergy. A drug provocation test was performed, and a hyperinflammatory response was observed. The patient received prednisolone (15 mg·day⁻¹) monotherapy; no further fever was observed during the subsequent 2 months. We therefore diagnosed azathioprine hypersensitivity syndrome. Under treatment with prednisolone (5 mg·day⁻¹) and mycophenolate mofetil (1 g·day⁻¹) (replacing the azathioprine), no signs of relapse or infection have occurred for more than two years. Renal function and the pulmonary lesions are stable, although the high MPO-ANCA titer and hematuria persist. The diagnosis of azathioprine hypersensitivity is often delayed because of the difficulty in identifying the relationship between immunosuppressive agents and hypersensitivity and in distinguishing this from infection or relapse of the primary disease. The misdiagnosis of azathioprine hypersensitivity leads to unnecessary treatment; thus, clinicians should consider allergic reactions specific to azathioprine when switching from induction to maintenance therapy.

Cutaneous manifestations in inflammatory bowel disease (Review)

Inflammatory bowel disease (IBD) is defined as a chronic condition characterized by unpredictable relapsing episodes of gastrointestinal inflammation. IBD is not limited to the gastrointestinal tract and should be considered a systemic disease which can involve any organ. Cutaneous manifestations in IBD are frequent and comprise a broad spectrum of diseases, ranging from mild to severe and sometimes debilitating lesions. Some of the cutaneous manifestations can present signs of an underlying intestinal disease, leading to the screening for non-detected IBD even in the absence of symptoms. Cutaneous EIMs are divided into 4 categories: i) Disease-specific lesions that show the same histopathologic findings as the underlying gastrointestinal disease, ii) reactive lesions which are inflammatory lesions that share a common pathogenetic mechanism but do not share the same pathology with the gastrointestinal disease, iii) associated conditions are more frequently observed in the context of IBD, without sharing the pathogenetic mechanism or the histopathological findings with the underlying disease and iv) drug-related skin reactions.

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.

Nonimmediate allergic reactions induced by Mesna

Mesna (2‐mercaptoethane sulfonate Na), a drug that alleviates cyclophosphamide (CYC)‐induced hemorrhagic cystitis, is frequently used to treat cancer and collagen diseases. A 33‐year‐old woman presented with high fever during CYC‐based induction therapy for systemic lupus erythematosus. Her final diagnosis was mesna‐induced drug hypersensitivity. Although mesna is widely used, allergic reactions are rare. This may be because of misdiagnosis as a primary disease flare‐up, infection, or CYC‐induced hypersensitivity reaction, which are commonly reported. Thus, accurate diagnosis is important for completion of the CYC‐based regimen.

Azathioprine Hypersensitivity Syndrome: Two Cases of Febrile Neutrophilic Dermatosis Induced by Azathioprine

Background

Azathioprine is an immunosuppressive agent used in the treatment of immune-mediated diseases. Azathioprine hypersensitivity syndrome is a rare adverse reaction occurring a few days to weeks after the administration of azathioprine.

Case 1

A 36-year-old male with ulcerative colitis presented with erythematous plaques, pustules and erosions on the lower back, buttocks and thighs associated with high fever (39°C) 2 weeks after the initiation of azathioprine 100 mg/day. Additional findings included leukocytosis (18.6 g/L) with neutrophilia (11.1 g/L) and elevated C-reactive protein (128 mg/L). Histopathology showed a dense infiltrate of neutrophils in the hair follicles. We increased the dose of prednisone to 1 mg/kg/day (60 mg/day) and azathioprine was discontinued. He had marked improvement within 3 weeks and did not have any relapse with a 1-year follow-up.

Case 2

A 57-year-old male with ulcerative colitis presented with erythematous plaques and pustules on the lower limbs associated with high fever (40°C) 1 week after the initiation of azathioprine 75 mg/day. Leukocytosis with neutrophilia (13.6 g/L) and elevated C-reactive protein (344 mg/L) were among the laboratory findings. Histopathology showed a dense infiltrate of neutrophils in the hair follicles. The dose of prednisone was increased to 20 mg/day and azathioprine was discontinued, which led to complete remission within 7 days. He did not have any relapse with a 6-month follow-up.

Conclusion

The development of acute neutrophilic dermatitis 2 weeks after the initiation of azathioprine and the complete resolution after its withdrawal were in favor of azathioprine hypersensitivity syndrome. It should not be confused with Sweet syndrome associated with inflammatory bowel disease, as maintenance of azathioprine treatment may lead to life-threatening reactions.

Cutaneous Manifestations of Crohn Disease

Awareness of the extraintestinal manifestations of Crohn disease is increasing in dermatology and gastroenterology, with enhanced identification of entities that range from granulomatous diseases recapitulating the underlying inflammatory bowel disease to reactive conditions and associated dermatoses. In this review, the underlying etiopathology of Crohn disease is discussed, and how this mirrors certain skin manifestations that present in a subset of patients is explored. The array of extraintestinal manifestations that do not share a similar pathology, but which are often seen in association with inflammatory bowel disease, is also discussed. Treatment and pathogenetic mechanisms, where available, are discussed.

Sweet syndrome on a patient with autoimmune hepatitis on azathioprine and CMV infection

Sweet syndrome (SS) is a rare inflammatory process presenting with painful erythematous skin eruptions, accompanied by fever and neutrophilia. It is associated with upper respiratory infection in fertile women (classic form), malignancy, infections, drugs and autoimmune diseases. Its pathogenesis remains to be determined. Nevertheless, cytokines may have a prominent role, due to a rapid response after corticosteroid administration. We describe a 32-year-old female with autoimmune hepatitis on azathioprine and prednisone, presenting with fever and inflammatory skin eruptions. Histologic examination of the skin lesions showed neutrophilic infiltrations of the dermis, confirming the diagnosis of SS. Concurrently, she tested borderline positive for recent CMV infection.

Sweet Syndrome: A Review and Update

Sweet syndrome is the most representative entity of febrile neutrophilic dermatoses. It typically presents in patients with pirexya, neutrophilia, painful tender erytomatous papules, nodules and plaques often distributed asymmetrically. Frequent sites include the face, neck and upper extremities. Affected sites show a characteristical neutrophilic infiltrate in the upper dermis. Its etiology remains elucidated, but it seems that can be mediated by a hypersensitivity reaction in which cytokines, followed by infiltration of neutrophils, may be involved. Systemic corticosteroids are the first-line of treatment in most cases. We present a concise review of the pathogenesis, classification, diagnosis and treatment update of this entity.

Three hospital admissions in 9 days to diagnose azathioprine hypersensitivity in a patient with Crohn's disease

Azathioprine (AZA) is commonly used as a steroid-sparing immunosuppressive medication for the treatment of immune-mediated disorders including Crohn's disease. There is ample awareness of the more common adverse effects of this drug, including myelosuppression and risk of malignancy. We present a case of a 57-year-old man with fistulizing Crohn's disease who underwent 3 hospital admissions for recurrent fever with an extensive work-up for infection before the diagnosis of AZA hypersensitivity was made. Clinicians should be vigilant for AZA hypersensitivity as a cause of otherwise unexplained fever. Furthermore, in patients with inflammatory bowel disease (IBD), the signs and symptoms of AZA hypersensitivity may overlap with typical findings of inflammatory bowel disease flare.