The histopathological spectrum of acute generalized exanthematous pustulosis (AGEP) and its differentiation from generalized pustular psoriasis

Patch tests in non-immediate cutaneous adverse drug reactions: Late readings on Day 4 is more sensitive than on Day 3

BACKGROUND

Patch tests (PTs) are recommended to identify the culprit drug in non-immediate cutaneous adverse drug reactions (NICADRs). We recently reported that, in patients with NICADRs, a unique reading of PTs at day (D)2 compared with an additional second late reading at D4 missed almost half (45.3%) of the positive PTs.

OBJECTIVES

To assess the change in sensitivity of the PT reading on D4 compared with the reading on D3.

METHODS

We performed a retrospective (July 2020-June 2023) monocentric study of patients who had PTs with two readings for a NICADR. We compared reading on D3 and the second reading on D4 for the suspected drug (primary outcome) and for the related drugs tested simultaneously (secondary outcome).

RESULTS

During the study period, 249 patients underwent patch testing with D3 and D4 readings. Regarding the primary outcome, the first reading at D3 was positive for 13.7% of patients, and the reading at D4 for 24.9% of patients (p < 0.0001). Regarding the secondary outcome, only 9.6% of patients had all their positive PT at D3 compared with 24.9% of patients at D4 (p < 0.0001). Considering the evaluated drug classes, no statistical difference was observed. However, we highlight that D3 reading detected all positive carbamazepine PTs (n = 3) while positive clindamycin PTs (n = 4) were identified only with the help of the second reading on D4.

CONCLUSION

This study showed that, an additional D4 reading compared with a single D3 reading enhanced the sensitivity of PTs to identify culprit drugs and related. Further studies should replicate these findings and evaluate the medico-economic balance and safety of a single reading of PTs on D4.

Prevalence, incidence, mortality, and healthcare resource use for generalised pustular psoriasis, palmoplantar pustulosis, and plaque psoriasis in England: a population-based cohort study

BACKGROUND

Generalised pustular psoriasis (GPP) and palmoplantar pustulosis (PPP) are chronic, inflammatory skin conditions. Accumulating evidence shows that GPP and PPP have different characteristics compared with plaque psoriasis and are distinct clinical entities.

OBJECTIVES

To assess the epidemiology, comorbidities, mortality and healthcare use for patients with GPP and PPP compared with those with plaque psoriasis in England.

METHODS

A cohort study involving analyses of longitudinal electronic health record data in the Clinical Practice Research Datalink Aurum database and linked hospital and mortality data between 2008 and 2019. The primary study outcome was the incidence and prevalence rates for GPP, PPP and plaque psoriasis in England. Secondary outcomes included survival rates and healthcare resource use (HCRU) by disease type.

RESULTS

We identified 373 patients with GPP, 1,828 with PPP and 224,223 with plaque psoriasis. The mean age was 55.9 years (standard deviation [SD]: 18.6) for patients with GPP, 51.5 years (SD: 16.4) for those with PPP, and 48.5 years (SD: 19.1) for those with plaque psoriasis; 62.5% and 65.9% of patients with GPP and PPP, respectively, were women, compared with 49.4% of those with plaque psoriasis. About half of the patients were overweight or obese at baseline (GPP, 48.6%; PPP, 56.0%; and plaque psoriasis, 45.9%). The incidence rates for GPP, PPP and plaque psoriasis were 0.25 (95% CI: 0.21-0.28), 2.01 (95% CI: 1.92-2.11) and 103.2 (95% CI: 102.5-103.9) per 100,000 person-years, respectively. From 2008 to 2019, the prevalence rates per 100,000 persons ranged from 1.61 to 3.0 for GPP, 1.1 to 18.7 for PPP and 1771.0 to 1903.8 for plaque psoriasis. Survival rates were lower for patients with GPP, particularly those who were over 55 years old and those with a history of ≥1 comorbidity in each cohort. HCRU was lower in the plaque psoriasis cohort and highest in the GPP cohort, particularly among those who had ≥1 GPP flare.

CONCLUSIONS

Our results provide further evidence that GPP is a distinct disease with different epidemiology, lower survival and higher HCRU than plaque psoriasis in England.

Acute generalized exanthematous pustulosis secondary to dose-related turmeric supplementation

We present the case of a 55-year-old woman with a 10-day history of a rapidly progressing generalized rash. History was significant for recent increase in turmeric supplement dose. Clinical presentation was notable for diffuse plate-like yellow scaling of the scalp with lesser involvement of the ears. On the trunk and extremities, erythematous circinate plaques studded with pustules were noted with central trailing scale and desquamation. Laboratory results showed slight elevation of white blood cell count from her baseline but within normal range. Histopathological analysis of two punch biopsies showed spongiotic dermatitis with eosinophils, and subcorneal pustules with eosinophils, respectively, without any organisms. These findings were most consistent with acute generalized exanthematous pustulosis (AGEP). Treatment included oral and topical corticosteroids as well as discontinuation of all dietary supplements. AGEP, a severe cutaneous adverse reaction, is associated most often with antibiotics; however, many other medications, including herbal supplements, have been documented as triggers in the literature. This is only the second reported case of potential turmeric-induced AGEP and the first reported case establishing a dose-related association between turmeric and AGEP. It is important to consider herbal supplements as part of the medical history to guide proper management when assessing a patient with AGEP.

Navigating IL-6: From molecular mechanisms to therapeutic breakthroughs

This concise review navigates the intricate realm of Interleukin-6 (IL-6), an important member of the cytokine family. Beginning with an introduction to cytokines, this narrative review unfolds with the historical journey of IL-6, illuminating its evolving significance. A crucial section unravels the three distinct signaling modes employed by IL-6, providing a foundational understanding of its versatile interactions within cellular landscapes. Moving deeper, the review meticulously dissects IL-6's signaling mechanisms, unraveling the complexities of its pleiotropic effects in both physiological responses and pathological conditions. A significant focus is dedicated to the essential role IL-6 plays in inflammatory diseases, offering insights into its associations and implications for various health conditions. The review also takes a therapeutic turn by exploring the emergence of anti-IL-6 monoclonal inhibitors, marking a profound stride in treatment modalities. Diving into the molecular realm, the review explores small molecules as agents for IL-6 inhibition, providing a nuanced perspective on diverse intervention strategies. As the review embarks on the final chapters, it contemplates future aspects, offering glimpses into potential research trajectories and the evolving landscape of IL-6-related studies.

Generalized Pustular Psoriasis, Acute Generalized Exanthematous Pustulosis, and Other Pustular Reactions: A Clinical Review

Generalized pustular rashes have various etiologies and can be challenging to diagnose and manage at first presentation. The authors provide an in-depth analysis of common pustular skin eruptions including generalized pustular psoriasis (GPP) and acute generalized exanthematous pustulosis, focusing on their pathophysiology, triggers, clinical presentation, diagnostic challenges, and management strategies. The article also highlights recent advances in genetic research and biologic therapies for GPP and the future directions in personalized medicine and prevention strategies.

The role of eosinophils in the differential diagnosis of inflammatory skin diseases

Eosinophils are known to be present in inflammatory skin diseases, but their diagnostic utility is not well established. Upon review of the published status of lesional eosinophils, several categories were identified. 1) Lesional eosinophils highly characteristic such that, in their absence, the pathologist may question the diagnosis. These include arthropod bite reactions and scabies, urticarial dermatitis, and other eosinophilic dermatoses. 2) Lesional eosinophils rare or absent, such that, in their presence, the pathologist may question the diagnosis. These include pityriasis lichenoides, graft versus host disease, and connective tissue disorders. 3) Lesional eosinophils variable and, while in some cases expected, are not required for diagnosis. These include drug reactions, atopic dermatitis and allergic contact dermatitis. 4) Lesional eosinophils variable and not expected but may be seen to a limited extent. These include lichen planus and psoriasis.

Current management of generalized pustular psoriasis

Generalized pustular psoriasis (GPP) is a rare subset of psoriasis involving episodes of sterile pustules accompanied by inflammation and, often, systemic involvement. The inflammatory nature of GPP has potential for severe multisystem complications including high-output cardiac failure, infections, digestive system issues, and disfiguring or lethal acute flare episodes. The disease tends to have higher prevalence in females and Asians. The IL-1/IL-36 inflammatory pathway is a critical facet of GPP's pathology. Genetic mutations that are associated with GPP include modifications of Interleukin 36 Receptor Antagonist (IL36RN), Caspase Recruitment Domain Family Member 14 (CARD14), Adaptor Related Protein Complex 1 Subunit Sigma 3 (AP1S3), Myeloperoxidase (MPO) and Serpin Peptidase Inhibitor Clade A Member 3 (SERPINA3) genes. Treatment guidelines for GPP are not well-entrenched. Currently, only one GPP-specific treatment, the interleukin-36 receptor antagonist (IL-36Ra) spesolimab, has been approved for use in the United States. Additional anti-IL-36 pathway therapies are currently being developed. Other treatment options include other biologic therapies such as IL-17 inhibitors, IL-23 inhibitors and TNFα inhibitors. Non-biologic therapeutic options include retinoids, cyclosporine and methotrexate. Treatment options differ throughout the world; most countries utilize retinoids, cyclosporine and methotrexate as first-line non-biologic options. China and United Kingdom have no GPP-specific biologic therapies approved for use, while several biologic therapies are approved for use in Japan. This review aims to serve as an update on the current global management of GPP while also including relevant aspects of disease pathogenesis, diagnosis, clinical presentation, histopathology, aetiology and epidemiology.

Acute Generalized Exanthematous Pustulosis: Clinical Features, Differential Diagnosis, and Management

Acute generalized exanthematous pustulosis (AGEP) is a rare, acute, severe cutaneous adverse reaction mainly attributed to drugs, although other triggers, including infections, vaccinations, ingestion of various substances, and spider bites, have also been described. AGEP is characterized by the development of edema and erythema followed by the eruption of multiple punctate, non-follicular, sterile pustules and subsequent desquamation. AGEP typically has a rapid onset and prompt resolution within a few weeks. The differential diagnoses for AGEP are broad and include infectious, inflammatory, and drug-induced etiologies. Diagnosis of AGEP depends on both clinical and histologic criteria, as cases of overlap with other disease processes have been reported. Management includes removal of the offending drug or treatment of the underlying cause, if necessary, and supportive care, as AGEP is a self-limited disease. This review aims to provide an overview and update on the epidemiology, pathogenesis, reported precipitating factors, differentials, diagnosis, and management of AGEP.

Pustular psoriasis of pregnancy: A rare cause of placental insufficiency

Generalised pustular psoriasis of pregnancy (GPPP) is a rare dermatosis that presents in the third trimester. It merits careful clinical assessment given the difficulty in diagnosis, impact on maternal health and association with placental insufficiency. We present a case of generalised pustulosis in a pregnant woman at 30 weeks gestation and describe the clinico-pathological challenges in obtaining a diagnosis of GPPP. Furthermore, we provide evidence from cardiotocography and ultrasound of evolving fetal compromise and describe how intensive management can facilitate a positive maternal–fetal outcome.

Pustular psoriasis with a focus on generalized pustular psoriasis: classification and diagnostic criteria. An Italian expert consensus

Generalized pustular psoriasis (GPP) is a severe and life-threatening systemic disease associated with significant morbidity and mortality. Recent progress has been made in understanding the pathogenetic pathways involved in GPP and an intricate interaction between innate and adaptive immune mechanisms has been suggested. Despite formal consensus guidelines on pustular psoriasis currently available in the literature, the definitions and classifications of GPP used across studies were inconsistent. Consequently, there are no unified criteria that can be universally adopted for precise diagnosis, classification and effective treatment of GPP patients with new targeted drugs. The aim of this review was to collect all the main evidence on available diagnostic criteria for GPP and to establish recommendations in order to promote a better stratification and therapeutic management of this severe and heterogeneous disease.

Tools to improve the diagnosis and management of T-cell mediated adverse drug reactions

Delayed drug T-cell immune-mediated hypersensitivity reactions have a large clinical heterogeneity varying from mild maculopapular exanthema (MPE) to severe cutaneous adverse reactions (SCARs) such as acute generalized exanthematous pustulosis (AGEP), drug reaction with eosinophilia and systemic symptoms (DRESS) and severe skin necrosis and blistering as seen in Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). Given the knowledge gaps related to the immunopathogenesis of these conditions, the absence of validated diagnostic tools and the significant associated morbidity and mortality, patients with SCARs often have limited drug choices. We performed a comprehensive review aiming to evaluate in vivo diagnostic tools such as delayed intradermal skin and patch testing and ex vivo/in vitro research assays such as the lymphocyte transformation test (LTT) and the enzyme-linked ImmunoSpot (ELISpot) assay. We searched through PubMed using the terms “drug allergy,” “in vivo” and “ex vivo” for original papers in the last 10 years. A detailed meticulous approach adapted to the various clinical phenotypes is recommended for the diagnostic and management of delayed drug hypersensitivity reactions. This review highlights the current diagnostic tools for the delayed drug hypersensitivity phenotypes.

Generalized pustular psoriasis: overview of the status quo and results of a panel discussion

Generalized pustular psoriasis (GPP) is a rare, severe, potentially life-threatening, autoinflammatory, neutrophilic skin disease that may be accompanied by fever and leukocytosis. This paper describes the current state of knowledge on GPP in terms of classification, (differential) diagnosis and prevalence. We present a comparison of the genetics and pathoimmunology of GPP and psoriasis vulgaris with the central mechanisms of autoimmunology and autoinflammation. The currently available therapeutic options, expert recommendations for therapy, and data from early clinical trials investigating targeted therapies will be summarized. We present the results of our discussion with 13 experts for psoriasis vulgaris and GPP and give an integrated overview of indication and therapy based on our personal experience and present an outlook on further research questions. Collectively, this article highlights the high unmet need in GPP, as there exists no satisfactory method of diagnosis or treatment to date and new treatment options will be of great therapeutic benefit to those affected.

First-Trimester Impetigo Herpetiformis Leads to Stillbirth: A Case Report

Introduction

Pustular psoriasis of pregnancy (PPP), also known as impetigo herpetiformis (IH), is a rare variant of generalized pustular psoriasis (GPP) in pregnancy. It typically occurs in the third trimester and is a life-threatening condition for both the pregnant mother and the fetus if not diagnosed and treated promptly. Drug-induced PPP has been reported in sporadic case reports. Here we present a case of first-trimester PPP occurring after applying drugs including chloroquine, which we consider a possible culprit triggering the disease.

Case report

A 29-year-old female was admitted to our department at 45 days gestation with sudden onset of fever and widespread erythematous pustules for 9 days. She had been on medications including hydroxychloroquine before onset. The eruptions and systemic symptoms were controlled with high-dose systemic steroids; however, she was detected to have a stillbirth, and underwent dilation and curettage of the uterine. At the latest follow-up about 2 years after her admission, she reported to have delivered a healthy baby about 1 month previously.

Conclusions

Chloroquine has potential to lead to PPP in the first trimester of pregnancy. Further studies are warranted to investigate the etiology and treatment of PPP to facilitate early recognition and optimal management of this relatively rare dermatosis in pregnancy.

Expression Profile of CD157 Reveals Functional Heterogeneity of Capillaries in Human Dermal Skin

CD157 acts as a receptor, regulating leukocyte trafficking and the binding of extracellular matrix components. However, the expression pattern and the role of CD157 in human blood (BEC) and the lymphatic endothelial cells (LEC) of human dermal microvascular cells (HDMEC), remain elusive. We demonstrated constitutive expression of CD157 on BEC and LEC, in fetal and juvenile/adult skin, in situ, as well as in isolated HDMEC. Interestingly, CD157 epitopes were mostly localized on BEC, co-expressing high levels of CD31 (CD31High), as compared to CD31Low BEC, whereas the podoplanin expression level on LEC did not affect CD157. Cultured HDMEC exhibited significantly higher numbers of CD157-positive LEC, as compared to BEC. Interestingly, separated CD157− and CD157+ HDMEC demonstrated no significant differences in clonal expansion in vitro, but they showed distinct expression levels of cell adhesion molecules, before and after cytokine stimulation in vitro. In particular, we proved the enhanced and specific adherence of CD11b-expressing human blood myeloid cells to CD157+ HDMEC fraction, using an in vitro immune-binding assay. Indeed, CD157 was also involved in chemotaxis and adhesion of CD11b/c monocytes/neutrophils in prevascularized dermo–epidermal skin substitutes (vascDESS) in vivo. Thus, our data attribute specific roles to endothelial CD157, in the regulation of innate immunity during inflammation.

Multisystem organ failure secondary to acute generalised exanthematous pustulosis (AGEP) with atypical presentation resembling septic shock

A woman was admitted for sepsis secondary to cellulitis. After clinical improvement of sepsis, non-follicular small pustules were observed on the trunk, limbs and face while vesicles/bullae and skin exfoliation were noted on upper extremities. Larger systemic manifestations included fever, hypertension and tachycardia. Laboratory results revealed neutrophilic leukocytosis, eosinophilia, mild transaminitis and acute renal failure. Despite treatment for potential sepsis and discontinuation of offending agents, her condition worsened leading to haemodynamic instability and renal failure requiring vasopressor support, intubation and continuous veno-venous haemodialysis. Skin biopsy revealed a diagnosis of acute generalised exanthematous pustulosis (AGEP), a rare condition usually caused by antibiotic treatment. The suspected offending drug was clindamycin, with possible combined effects by metronidazole and/or vancomycin. Improvement of skin manifestations were seen within 48 hours of starting systemic steroids. Here, we present an uncharacteristic case of AGEP clinically presenting with atypical skin lesions, severe systemic involvement mimicking septic shock, which culminated in multisystem organ failure.

Results of patch testing in Acute generalized exanthematous pustulosis (AGEP): a literature review

The literature on positive patch test results in acute generalized exanthematous pustulosis (AGEP) is reviewed. 93 drugs were identified that have together caused 259 positive patch tests in 248 patients suffering from AGEP. The drug classes causing the highest number of reactions are beta-lactam antibiotics (25.9%), other antibiotics (20.8%), iodinated contrast media (7.3%) and corticosteroids (5.4%), together accounting for nearly 60% of all reactions. The highest number of reactions to individual drugs was to amoxicillin (n=36), followed by pristinamycin (n=25), diltiazem (n=14), amoxicillin-clavulanic acid (n=13), clindamycin (n=11) and iomeprol (n=8); 59 of the 93 drugs each caused a single case only. The "Top-10" drugs together caused over 50% of all reactions. The sensitivity of patch testing (percentage of positive reactions) in patients with AGEP is largely unknown, but may generally be around 50%, which also applies to pristinamycin. Patch testing in AGEP appears to be safe, although mild recurrence of AGEP skin symptoms or other rashes may occur occasionally. Clinical aspects of AGEP, including epidemiology, etiology and pathophysiology, clinical features, histology, treatment, and prognosis are briefly presented, as are diagnosing the disease and identifying the culprit drugs with patch tests, intradermal tests, in vitro tests, and challenge tests. This article is protected by copyright. All rights reserved.

Clinical Course and Characteristics of Generalized Pustular Psoriasis

Generalized pustular psoriasis (GPP) is a rare, potentially life-threatening disease characterized by episodes of widespread sterile macroscopic pustules, with or without systemic inflammation and/or plaque psoriasis. Multiple GPP subtypes have been described, from acute GPP of von Zumbusch to milder, annular pustular psoriasis. Generalized pustular psoriasis mainly affects adults, with a female preponderance, but juvenile GPP also occurs. Flares are a hallmark of GPP and may occur de novo or be provoked by triggers, including withdrawal of systemic corticosteroids, infections, stress, pregnancy, and menstruation. Severity of flares varies widely between patients, and between flares in an individual patient. Significant flares are often accompanied by systemic symptoms, notably fever, general malaise, and extracutaneous manifestations such as arthritis, uveitis, and neutrophilic cholangitis. Common laboratory abnormalities include neutrophilia, elevated C-reactive protein levels, hypocalcemia, and abnormal liver function tests. The clinical course of GPP is highly variable; it can be a relapsing disease with recurrent flares and no pustulation between flares or a persistent disease with perpetual mild pustulation punctuated with flares of greater severity. Patients may have multiple flares per year or a flare every few years. Most flares last 2–5 weeks and approximately 50% require hospitalization. Life-threatening complications include sepsis and renal, hepatic, respiratory, and heart failure. Reported mortality rates are 2–16%.

Diagnosis of Generalized Pustular Psoriasis

Generalized pustular psoriasis (GPP) is a severe rare skin disease characterized by widespread eruption of sterile superficial macroscopic pustules with or without systemic inflammation. Generalized pustular psoriasis flares may lead to life-threatening multiorgan complications, which highlights the need for rapid and accurate diagnosis. However, the rarity of the disease and its heterogeneous cutaneous and extracutaneous symptoms, and the resemblance of symptoms to other skin conditions, pose considerable challenges to the timely diagnosis and treatment of patients with GPP. Current laboratory tests used for GPP diagnosis are generally not GPP specific, and are mainly focused on the assessment of inflammatory markers and clinical and histopathologic features of GPP, and emerging genetic screening approaches. A differential diagnosis to distinguish GPP from other similar conditions requires careful assessment of the patient’s skin symptoms, potential disease triggers, medical history, histopathologic features, laboratory tests, and clinical disease course. The comprehensive interpretation of these assessments can be challenging owing to the lack of standardized global guidelines. While there is currently a lack of standardized international guidelines for the diagnosis of GPP, recent advances in our understanding of the genetics and pathogenesis of the disease have provided new opportunities to enhance diagnosis. In the future, defining specific GPP subtypes using genetic and histopathologic strategies will guide therapeutic decisions, allowing patients to achieve their treatment goals without delay. In this article, we provide an overview of the current diagnostic methods, differential diagnostic strategies, and future advances in the diagnosis of GPP, as well as features of GPP variants.

Pathophysiology of Generalized Pustular Psoriasis

Generalized pustular psoriasis (GPP) is a rare, severe form of pustular psoriasis characterized by widespread, recurrent episodes of neutrophil-rich pustule formation in the epidermis, which can be accompanied by fever and systemic inflammation. Recent clinical, histologic, and genetic evidence indicates that GPP is a distinct entity from plaque psoriasis, with different cytokine pathways predominant in the manifestation of each disease. The interleukin-36 (IL-36) signaling cascade plays a key role in regulating the innate immune system, and its dysregulation appears central to the pathogenesis of GPP. The altered expression of various IL-36 pathway constituents has been shown to cause a positive feedback loop of uncontrolled signaling and excess production of inflammatory cytokines, which in turn leads to chemokine induction and neutrophil recruitment in the epidermis. Given the potentially life-threatening nature of GPP episodes, drug interventions that rapidly achieve disease resolution are required. Early phase data indicate that treatments targeting various components of the IL-36 inflammatory cascade represent promising areas of research. However, there are currently no therapeutic agents specifically approved for GPP in the USA or Europe. Understanding the inflammatory pathways, associated risk factors, and role of neutrophils in the manifestation and perpetuation of GPP flares remains a key goal in developing effective therapeutics. In this article, we summarize the current understanding of GPP, describe novel therapeutic opportunities, and detail how the unique pathophysiology of the disease may inform future treatment strategies.

Unmet Educational Needs and Clinical Practice Gaps in the Management of Generalized Pustular Psoriasis: Global Perspectives from the Front Line

INTRODUCTION

Generalized pustular psoriasis (GPP) is a rare, potentially life-threatening, neutrophilic, autoinflammatory skin disease characterised by recurrent flares of generalised sterile pustules and associated systemic features. Inconsistent diagnostic criteria and a lack of approved therapies pose serious challenges to GPP management. Our objectives were to discuss the challenges encountered in the care of patients with GPP and identify healthcare provider (HCP) educational needs and clinical practice gaps in GPP management.

METHODS

On 24 July 2020, 13 dermatologists from 10 countries (Brazil, Canada, China, Egypt, France, Germany, Japan, Malaysia, the UK and the USA) attended a workshop to share experiences in managing patients with GPP. Educational needs and clinical practice gaps grouped according to healthcare system level were discussed and ranked using interactive polling.

RESULTS

Lack of experience of GPP among HCPs was identified as an important individual HCP-level clinical practice gap. Limited understanding of the presentation and pathogenesis of GPP among non-specialists means misdiagnosis is common, delaying referral and treatment. In countries where patients may present to general practitioners or emergency department HCPs, GPP is often mistaken for an infection. Among dermatologists who can accurately diagnose GPP, limited knowledge of treatments may necessitate referral to a colleague with more experience in GPP. At the organisational level, important needs identified were educating emergency department HCPs to recognise GPP as an autoinflammatory disease and improving communication, cooperation and definitions of roles within multidisciplinary teams supporting patients with GPP. At the regulatory level, robust clinical trial data, clear and consistent treatment guidelines and approved therapies were identified as high priorities.

CONCLUSIONS

The educational imperative most consistently identified across the participating countries is for HCPs to understand that GPP can be life-threatening if appropriate treatment initiation is delayed, and to recognise when to refer patients to a colleague with more experience of GPP management.

Generalized pustular psoriasis (von Zumbusch)

Generalized pustular psoriasis (von Zumbusch) is a rare and acute eruption characterized by multiple sterile pustules over an erythematous and edematous background, eventually associated with psoriasis vulgaris. Classically, it manifests as a potentially severe systemic picture and demands prompt diagnosis and intervention. The duration of each flare-up and intervals between the pustular episodes is extremely variable. Recently, genetic abnormalities have been identified mainly in the familial and early variants of this disease. The therapeutic arsenal is limited; however, new drugs being evaluated aim to control both pustular flare-ups and disease recurrences.

Pustular Psoriasis: From Pathophysiology to Treatment

Pustular psoriasis (PP) is a clinicopathological entity encompassing different variants, i.e., acute generalized PP (GPP), PP of pregnancy (impetigo herpetiformis), annular (and circinate) PP, infantile/juvenile PP, palmoplantar PP/palmoplantar pustulosis, and acrodermatitis continua of Hallopeau (ACH), which have in common an eruption of superficial sterile pustules on an erythematous base. Unlike psoriasis vulgaris, in which a key role is played by the adaptive immune system and interleukin (IL)-17/IL-23 axis, PP seems to be characterized by an intense inflammatory response resulting from innate immunity hyperactivation, with prominent involvement of the IL-36 axis. Some nosological aspects of PP are still controversial and debated. Moreover, owing to the rarity and heterogeneity of PP forms, data on prognosis and therapeutic management are limited. Recent progresses in the identification of genetic mutations and immunological mechanisms have promoted a better understanding of PP pathogenesis and might have important consequences on diagnostic refinement and treatment. In this narrative review, current findings in the pathogenesis, classification, clinical features, and therapeutic management of PP are briefly discussed.

Generalized Pustular Psoriasis: Divergence of Innate and Adaptive Immunity

Generalized pustular psoriasis (GPP) is a severe, relapsing, immune-mediated disease characterized by the presence of multiple sterile pustules all over the body. The exact pathomechanisms behind GPP remain elusive, although increased interest in the genetic basis and immunological disturbances have provided some revealing insights into the underlying signaling pathways and their mutual interaction. The genetic background of GPP has been thoroughly investigated over the past few years. The conducted studies have identified genetic variants that predispose to pustular forms of psoriasis. The loss-of-function mutation of the interleukin 36 receptor antagonist gene, along with rare gain-of-function mutations in the gene that encodes the keratinocyte signaling molecule (CARD14), are examples of the uncovered abnormalities. Interleukin 36 (IL-36), along with neutrophils, is now considered a central cytokine in GPP pathogenesis, with IL-36 signaling providing a link between innate and adaptive immune responses. More recently, a new concept of inflammation, caused by a predominantly genetically determined abnormal activation of innate immune response and leading to inflammatory keratinization, has arisen. GPP is currently considered a representative of this novel group of skin conditions, called autoinflammatory keratinization diseases. As no therapeutic agents have been approved for GPP to date in the United States and Europe, the novel anti-IL-36R antibodies are particularly promising and may revolutionize management of the disease.

Acute generalized exanthematous pustulosis in children and adolescents in Singapore: A ten-year retrospective review

BACKGROUND

Acute generalized exanthematous pustulosis (AGEP) is a rare, severe, cutaneous adverse reaction. Although most commonly caused by drugs, it can also be triggered by infections, especially in children.

METHODS

This is a retrospective study involving children and adolescents aged 16 years or younger, diagnosed with AGEP between January 2010 and March 2020 in our tertiary pediatric hospital. Information pertaining to the patient's demographics, clinical presentation and progress, biochemical, microbiological, and histopathological investigations, treatment, and outcomes was analyzed.

RESULTS

Eight patients were diagnosed with AGEP with mean age 8.2 years (range: 1.7-16.0 years). None of the patients had a personal or family history of psoriasis. Almost all patients had fever (n = 7, 87.5%). Although all 8 patients had intercurrent illness, 5 cases were attributed to infection, while the other 3 were likely precipitated by drugs. Abnormal hematological and biochemical parameters included a raised absolute neutrophil count (mean: 11.5 × 10⁹ /L, range: 5.0-30.9 × 10⁹ /L), C-reactive protein (mean: 52.5 mg/L, range: 5.0-143.7 mg/L), and erythrocyte sedimentation rate (mean: 38.6 mm/h, range: 6-64 mm/h). All patients developed post-pustular desquamation and subsequently recovered. The mean duration from onset to cessation of acute pustulation was 5.6 days (range: 3.0-10.0 days). One patient developed a recurrent episode of AGEP.

CONCLUSION

AGEP is rare and may be more commonly caused by infections in children. The condition is self-limiting with overall good outcomes in this age-group. In cases with concomitant infection and drug use, formal allergy testing should be arranged after resolution of the infection to confirm the underlying etiology.

Hydroxychloroquine-induced acute generalized exanthematous pustulosis: a series of seven patients and review of the literature

BACKGROUND

Hydroxychloroquine (HCQ)-induced acute generalized exanthematous pustulosis (AGEP) is poorly described in the literature. The aim of our study was to characterize the clinical, laboratory, allergological, and genetic features of HCQ-induced AGEP.

METHODS

We conducted a retrospective study of patients with HCQ-induced AGEP diagnosed between 2011 and 2019. We performed molecular analysis to identify variations in the IL36RN gene. We also reviewed similar cases reported between 1991 and March 2020.

RESULTS

Seven female patients were included. The mean age was 47 years old, and the average time from HCQ start to onset of symptoms was 40 days. All patients received topical steroids with a full resolution of the rash within an average of 39 days after HCQ withdrawal. Patch tests were performed for three patients with positive results in one case. Genetic analyses were performed for three patients, and no mutation in the IL36RN gene was identified.

CONCLUSION

The latent period and the duration for resolution of HCQ-induced AGEP may be longer than with other drugs due to the metabolic characteristics of HCQ. Mutations in the IL36RN gene were not identified in our patients.

A brief guide to pustular psoriasis for primary care providers

Pustular psoriasis refers to a heterogeneous group of chronic inflammatory skin disorders that are clinically, histologically, and genetically distinct from plaque psoriasis. Pustular psoriasis may present as a recurrent systemic illness (generalized pustular psoriasis [GPP]), or as localized disease affecting the palms and/or soles (palmoplantar pustulosis [PPP], also known as palmoplantar pustular psoriasis), or the digits/nail beds (acrodermatitis continua of Hallopeau [ACH]). These conditions are rare, but their possible severity and consequences should not be underestimated. GPP, especially an acute episode (flare), may be a medical emergency, with potentially life-threatening complications. PPP and ACH are often debilitating conditions. PPP is associated with impaired health-related quality of life and psychiatric morbidity, while ACH threatens irreversible nail and/or bone damage. These conditions can be difficult to diagnose; thus, primary care providers should not hesitate to contact a dermatologist for advice and/or patient referral. The role of corticosteroids in triggering and leading to flares of GPP should also be noted, and physicians should avoid the use of systemic corticosteroids in the management of any form of psoriasis.

Clinical Presentation and Management of Atypical and Recalcitrant Acute Generalized Exanthematous Pustulosis (AGEP)

Acute generalized exanthematous pustulosis (AGEP) is a severe cutaneous adverse reaction (SCAR) characterized by sterile non-follicular pustules on an erythematous base that form rapidly after drug exposure. AGEP is mediated by numerous cytokines produced by drug specific T-cells that mediate neutrophilic intracorneal, subcorneal, and/or intraepidermal pustule development. Though genetic susceptibility is not fully understood, individuals with mutations in IL-36RN may be at increased risk of AGEP development. AGEP commonly presents with leukocytosis and fever in the acute pustular phase and follows a self-limited desquamative recovery phase upon removal of offending drug. Severe cases of AGEP may have multisystem organ involvement. Atypical presentations of AGEP include localized eruptions and cases with overlapping clinical and histopathological features associated with Stevens-Johnson syndrome/toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms, and generalized pustular psoriasis. Most cases of AGEP clear rapidly with systemic corticosteroids, but severe or recalcitrant cases may require other systemic therapies such as cyclosporine, and intravenous immunoglobulin.

Fluconazole-induced acute generalized exanthematous pustulosis

Acute generalized exanthematous pustulosis (AGEP) is a rare severe cutaneous adverse reaction usually caused by drugs. The annual incidence is one to five cases per million. It is characterized by an acute febrile episode, accompanied by numerous small primarily non-follicular, sterile pustules arising within large areas of edematous erythema. There have been several case reports to date of AGEP following exposure to antifungals. Terbinafine is most commonly implicated in AGEP. We report a case of 7-year-old boy who developed AGEP shortly after commencing oral fluconazole for Tinea capitis. To our knowledge, this is the fourth reported case of AGEP due to fluconazole.

Generalized Pustular Psoriasis: Clinical Management and Update on Autoinflammatory Aspects

Generalized pustular psoriasis (GPP) is a chronic, systemic inflammatory disease accompanied by high fever and general malaise. Diffuse erythema and swelling of the extremities occur, with multiple sterile pustules all over the body in GPP patients. GPP often relapses over the lifetime and can be life-threatening. Recent discoveries of the underlying molecular genetic basis of many cases of this disorder have provided major advances to clinicians and researchers towards an understanding of the pathomechanism of GPP. However, the therapeutic management of GPP still faces many challenges and much uncertainty, and an evidence-based review summarizing the available clinical data on the management of this heterogeneous disease is needed. The present review addresses challenges regarding the precise clinical diagnosis and evaluation of clinical symptoms in GPP. In addition, we update and briefly summarize the current understanding of molecular pathomechanisms behind GPP as an autoinflammatory keratinization disease. Recent publications have clarified the genetic backgrounds of patients with GPP and ethnic differences in predisposing factors. Although there are ethnic differences in the prevalences of these pathogenic alleles, from recent reports, at most 60.5% (IL36RN), 5.9% (CARD14), and 10.8% (AP1S3) of GPP patients have the mutations/variations of these genes. All the reported biologics studied seemed effective and relatively well tolerated. Although it is difficult to evaluate therapeutic efficacy from studies on just a few cases, recent findings suggest that biologics can be a useful, powerful tool for controlling skin and systemic inflammation in GPP and for improving the quality of life of GPP patients.

Clinical Phenotypes of Severe Cutaneous Drug Hypersensitivity Reactions

Drug hypersensitivity reactions are clinically heterogenous ranging from mild to severe. Most drug hypersensitivity reactions are accompanied by cutaneous manifestations. Fever, mucous membrane involvement, large blisters, facial oedema, pustulosis and visceral involvement are clinical features that lead to suspicion of severe adverse drug reactions. Severe cutaneous adverse drug reactions (SCARs) include Stevens-Johnson syndrome, toxic epidermal necrolysis, drug rash eosinophilia and systemic symptoms, acute generalized exanthematous pustulosis. Serum sickness like reactions, drug induced vasculitis and generalized bullous fixed drug eruptions are less severe clinical entities. SCARs are uncommon but associated with significant morbidity and mortality. Physician should be aware of specific red flags and danger signs to immediately identify these reactions. Immediate drug withdrawal is mandatory. Early diagnosis and appropriate treatment significantly affect the prognosis of the disease. The purpose of our review is to discuss clinical phenotypes of severe cutaneous drug hypersensitivity reactions.

Diagnosis and screening of patients with generalized pustular psoriasis

Generalized pustular psoriasis (GPP) is a rare and potentially life-threatening variant of psoriasis that is characterized by recurrent, acute onset, widely distributed pustular eruptions on inflamed, erythematous skin. It is important to recognize acute GPP as a subtype of psoriasis associated with high morbidity and mortality so therapy can be initiated without delay. Since GPP was first described in 1910 by Leopold von Zumbusch, it has been inconsistently defined, stratified, and diagnosed in the literature. Multiple definitions and diagnostic criteria have been proposed over the years. Recently, formal consensus guidelines on GPP have been published by international groups. This article reviews the current evidence and understanding in the diagnosis and screening of GPP.

Distinguishing pustular psoriasis and acute generalized exanthematous pustulosis on the basis of plasmacytoid dendritic cells and MxA protein

BACKGROUND

Distinguishing acute generalized exanthematous pustulosis (AGEP) and pustular psoriasis (PS) can be challenging. Staining for plasmacytoid dendritic cells, or PDCs (producer of IFN-α/β), and MxA (an IFN-α/β inducible protein) may help discriminate these entities.

METHODS

Forty-three cases of AGEP and PS were compiled from two academic institutions. All cases were examined for CD123+ PDCs, eosinophils, acanthosis, papillomatosis, suprapapillary plate thinning, tortuous dilated capillaries, single necrotic keratinocytes, papillary dermal edema, vasculitis, eosinophil exocytosis, intraepidermal pustules, and subcorneal pustules. A subset of cases (n = 26) was stained for MxA.

RESULTS

Perivascular and intraepidermal PDCs, dilated tortuous vessels, and MxA expression in the dermal inflammatory infiltrate were significantly (P < 0.05) in favor of a diagnosis of PS. The absence of PDCs and presence of eosinophils favored a diagnosis of AGEP (P < 0.05).

CONCLUSIONS

We found compelling evidence for the use of CD123 to highlight PDCs in these cases. The presence of PDCs and expression of MxA in dermal inflammatory infiltrate, as well as absence of eosinophils and presence of tortuous dilated capillaries favored a diagnosis of PS. Expression of MxA in the dermal infiltrate corresponds with a Th1 pathway in PS and may indicate a Th1 component in the early initial phase of AGEP.

Acute generalized exanthematous pustulosis and psoriasis: what can be learned from comorbidities

BACKGROUND

Acute generalized exanthematous pustulosis (AGEP) is a rare pustular severe cutaneous adverse reaction. Differentiating between AGEP and pustular psoriasis may represent a diagnostic challenge. We sought to evaluate the prevalence of comorbidities in a series of patients with AGEP compared to a series of patients with psoriasis vulgaris and to a series of patients with drug-related psoriasis.

METHODS

Medical records of 14 patients with AGEP, 33 patients with psoriasis vulgaris, and 18 patients with drug-related psoriasis were reviewed. The presence of comorbidities was recorded, and a comparative analysis was performed.

RESULTS

A personal history of psoriasis was present in 4 (28%) patients with AGEP compared to 12 (66%) patients with drug-related psoriasis (Pv=0.03). The prevalence of psoriasis-related morbidities was significantly lower in the AGEP group compared to the psoriasis group and to the drug-related psoriasis group (Pv<0.01, 0.05, respectively). Each of the psoriasis-related morbidities had significantly lower prevalence in the AGEP group compared to the psoriasis group and to the drug-related psoriasis group (Pv<0.01).

CONCLUSIONS

In conclusion, differences between AGEP, psoriasis vulgaris, and drug-related psoriasis regarding the prevalence of psoriasis-related morbidities may assist differentiation in borderline cases.

A case of prolonged generalized exanthematous pustulosis caused by hydroxychloroquine-Literature review

Acute generalized exanthematous pustulosis (AGEP) is a self-limited drug reaction. Hydroxychloroquine (HCQ) is an uncommon cause of AGEP with a prolonged recovery course; Thus, the physicians should take the possibility of this rare but severe event in their minds and try to diagnose correctly and better management.

Codeine-induced acute generalized exanthematous pustulosis without IL36RN mutations

Recent studies have suggested an association between mutations in the IL-36RN gene and the onset of pustular generalized. In the literature, only one case of acute generalized exanthematous pustulosis (AGEP) induced by codeine in a patient with IL36RN mutation has been reported. Herein, we reported an unusual case of AGEP caused by codeine in a patient with a history of psoriasis and confirmed by an oral provocation test. In this case, we have shown that the IL36RN gene mutation is not a constant condition in drug-induced AGEP. Clinicians should be aware of this side effect of codeine especially, in patients with a history of psoriasis. More studies are needed to clarify the association between drug-induced AGEP and IL36RN gene mutations.