Crucial Role of Viral Reactivation in the Development of Severe Drug Eruptions: a Comprehensive Review

Recent advances in the diagnosis and treatment of DIHS/DRESS in 2025

Drug-induced hypersensitivity syndrome (DIHS) or drug reaction with eosinophilia and systemic symptoms (DRESS) is a severe drug reaction characterized by a range of clinical manifestations. These range from mild cases resolving upon cessation of the causative drug to severe cases involving complex disease progression and potential fatality. A hallmark of DIHS/DRESS is the sequential reactivation of herpesviruses, particularly human herpesvirus 6 (HHV-6), during the disease course, contributing to recurrent symptoms. Viral reactivation can lead to critical complications, including infectious DIHS/DRESS-associated complications (iDACs) and autoimmune sequelae (aDACs). Managing DIHS/DRESS remains challenging due to its complexity, requiring precise prediction and tailored treatment strategies. Recent studies suggest that early-stage classification using the DIHS/DRESS Severity (DDS) score may help identify refractory cases, including DACs. Furthermore, early intervention with anti-cytomegalovirus (anti-CMV) therapy can mitigate iDACs caused by CMV reactivation, preventing progression to severe CMV-related diseases. Long-term follow-up is crucial, as aDACs can manifest even 3 years postonset. Serial monitoring is recommended, particularly in patients treated with intravenous immunoglobulin or corticosteroid pulse therapy, which are recognized risk factors for aDAC development. This review highlights DIHS/DRESS management strategies, focusing on its clinical features, the role of viral reactivation, and therapeutic interventions.

Novel insights into molecular and cellular aspects of delayed drug hypersensitivity reactions

INTRODUCTION

Delayed drug hypersensitivity reactions (DDHRs) represent a major health problem. They are unpredictable and can cause life-long disability or even death. The pathophysiology of DDHRs is complicated, multifactorial, and not well understood mainly due to the lack of validated animal models or in vitro systems. The role of the immune system is well demonstrated but its exact pathophysiology still a matter of debate.

AREA COVERED

This review summarizes the current understanding of DDHRs pathophysiology and abridges the available new evidence supporting each hypothesis. A comprehensive literature search for relevant publications was performed using PubMed, Google Scholar, and Medline databases with no date restrictions and focusing on the most recent 10 years.

EXPERT OPINION

Although multiple milestones have been achieved in our understanding of DDHRs pathophysiology as a result of the development of useful experimental models, many questions are yet to be fully answered. A deeper understanding of the mechanistic basis of DDHRs would not only facilitate the development of robust and reliable diagnostic assays for diagnosis, but would also inform therapy by providing specific target(s) for immunomodulation and potentially permit pre-therapeutic risk assessment to pursue the common goal of safe and effective drug therapy.

Atypical drug-induced hypersensitivity syndrome with multiple organ failure rescued by combined acute blood purification therapy: a case report

BACKGROUND

Drug-induced hypersensitivity syndrome (DIHS), including Stevens-Johnson syndrome (SJS), is a severe rash that often develops 2-6 weeks after the intake of the causative drug; however, its diagnosis is sometimes difficult. This article describes a case in which a patient with DIHS-induced multiple organ failure was successfully treated with blood purification therapy.

CASE PRESENTATION

A male patient in his 60s was admitted to our hospital with autoimmune encephalitis. The patient was treated with steroid pulse therapy, acyclovir, levetiracetam, and phenytoin. From the 25th day, he presented with fever (≥ 38 °C) as well as miliary-sized erythema on the extremities and trunk, followed by erosions. DIHS and SJS were suspected; accordingly, levetiracetam, phenytoin, and acyclovir were discontinued. On the 30th day, his condition further deteriorated, and he was admitted to the intensive care unit for ventilatory management. The next day, he developed multi-organ failure and was started on hemodiafiltration (HDF) for acute kidney injury. Although he presented with hepatic dysfunction and the appearance of atypical lymphocytes, he did not meet the diagnostic criteria for DIHS or SJS/toxic epidermal necrolysis. Therefore, he was diagnosed with multi-organ failure caused by severe drug eruption and underwent a 3-day treatment with plasma exchange (PE) in addition to HDF. Accordingly, the patient was diagnosed with atypical DIHS. After being started on blood purification therapy, the skin rash began to disappear; moreover, the organ damage improved, with a gradual increase in urine output. Eventually, the patient was weaned off the ventilator and transferred to the hospital on the 101st day.

CONCLUSIONS

HDF + PE could effectively treat multi-organ failure caused by atypical DIHS, which is difficult to diagnose.

Case report: Severe non-pigmenting fixed drug eruption showing general symptoms caused by chondroitin sulfate sodium

Non-pigmenting fixed drug eruption (NPFDE) is a subtype of fixed drug eruption (FDE) in which repeated eruptions occur at the same site. Clinically, NPFDE disappears without pigmentation changes; however, it sometimes causes fever or arthralgia. Its histopathological characteristics reportedly include infiltrations of CD8-positive T cells with a paucity of melanocytes as compared to FDE. We present the first case of severe NPFDE exhibiting general symptoms caused by chondroitin sulfate sodium. The patient was a 44-year-old man. Intravenous injection of chondroitin sulfate sodium caused erythema in the affected area. A histopathological examination of the biopsy tissue revealed infiltration of CD3-positive lymphocytes (both CD4-positive and CD8-positive lymphocytes) into the epidermis, minimal liquefaction degeneration in the basal layer of the epidermis, and few dermal melanophages, which may be responsible for non-pigmentation.

Risk of progression to autoimmune disease in severe drug eruption: risk factors and the factor-guided stratification

The identification of risk factors is key not only to uncover the pathogenesis of autoimmune disease but also to predict progression to autoimmune disease. Drug-induced hypersensitivity syndrome (DiHS)/ drug reaction with eosinophilia and systemic symptoms (DRESS) is likely the best prototypic example for analyzing the sequential events. We conducted a retrospective study of 55 patients with DiHS/DRESS followed for the possibility of later development of autoimmune disease ∼18 years after resolution. Nine patients progressed to autoimmune sequelae regardless of treatment. The generation of autoantibodies preceded by 8 years in 8 of the 9 patients. The combination of increases in lymphocyte counts, severe liver damage, a rebound increase in globulin, persistent reactivations of Epstein-Barr virus and human herpesvirus-6, and low interleukin (IL)-2 and IL-4 at the acute/subacute phases, were significant risk factors for the future development of autoimmune disease. Based on these factors, we established a scoring system that can identify high-risk patients. When stratified these patients into three risk categories (low/intermediate/high), occurrence of autoimmune disease was exclusively detected in the high group. Our data represent the new scoring system to identify patients at high-risk of developing autoimmune disease, although a larger study is required to validate the scoring system.

Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS): Series of 49 French Pediatric Cases

BACKGROUND

Drug reaction with eosinophilia and systemic symptoms (DRESS) is a rare and potentially fatal adverse reaction. It can be difficult to diagnose, even more so among children, because symptoms may mimic other commonly encountered pediatric conditions.

OBJECTIVE

To describe clinical and laboratory features of DRESS syndrome in the pediatric population (age ≤18 years) and establish causative agents and treatment modalities.

METHODS

This was a multicenter retrospective study of probable and definite DRESS cases (Registry of Sever Cutaneous Adverse Reaction score ≥ 4) in children hospitalized in 15 French university hospitals between 2000 and 2020.

RESULTS

We included 49 cases. All children had fever and rash, 69.4% had lymphadenopathy, and 65.3% had facial edema. The most common organ affected was the liver (83.7%). Treatment consisted of topical corticosteroid in only 30.6% and systemic corticosteroid in 55.1%; 12.2% received intravenous immunoglobulin. Among probable and likely culprit drugs, 65% were antibiotics and 27.5% were antiepileptics, median time to DRESS symptom onset after initiation of 15 days (13 days with antibiotics and 21 days with antiepileptics). Twenty-seven children had allergy assessment for causative agents, 65.4% of whom had positive tests.

CONCLUSIONS

Culprit drugs are frequently antibiotics and antiepileptic drugs, and onset is often less than 2 weeks after treatment starts, especially with antibiotics. Treatment with topical corticosteroids appears to be sufficient in the least severe cases. Treatment by systemic corticosteroid therapy remains the reference treatment in case of severe organ damage.

Long-term skin-resident memory T cells proliferate in situ and are involved in human graft-versus-host disease

The skin contains a population of tissue-resident memory T cells (Trm) that is thought to contribute to local tissue homeostasis and protection against environmental injuries. Although information about the regulation, survival program, and pathophysiological roles of Trm has been obtained from murine studies, little is known about the biology of human cutaneous Trm Here, we showed that host-derived CD69+ αβ memory T cell clones in the epidermis and dermis remain stable and functionally competent for at least 10 years in patients with allogeneic hematopoietic stem cell transplantation. Single-cell RNA sequencing revealed low expression of genes encoding tissue egress molecules by long-term persisting Trm in the skin, whereas tissue retention molecules and stem cell markers were displayed by Trm The transcription factor RUNX3 and the surface molecule galectin-3 were preferentially expressed by host T cells at the RNA and protein levels, suggesting two new markers for human skin Trm Furthermore, skin lesions from patients developing graft-versus-host disease (GVHD) showed a large number of cytokine-producing host-derived Trm, suggesting a contribution of these cells to the pathogenesis of GVHD. Together, our studies highlighted the relationship between the local human skin environment and long-term persisting Trm, which differs from murine skin. Our results also indicated that local tissue inflammation occurs through host-derived Trm after allogeneic hematopoietic stem cell transplantation.

Fixed Drug Eruptions: An Update, Emphasizing the Potentially Lethal Generalized Bullous Fixed Drug Eruption

A fixed drug eruption (FDE) is a relatively common reaction associated with more than 100 medications. It is defined as a same-site recurrence with exposure to a particular medication. The primary approach and treatment for all types of FDEs are to identify and remove the causative agent, often accomplished by a thorough history of medication and other chemical exposures, and possibly prior episodes. The most common category of FDE, localized FDE, whether bullous or non-bullous, is self-limited. Although one can confirm the causative agent using oral challenge testing, it is not recommended due to the risk of severe exacerbation or possible generalization; patch testing is now preferred. Bullous FDE may resemble erythema multiforme. Treatment of localized FDE includes medication removal, patient counseling, and symptomatic relief. Failure to remove the causative agent in localized FDE can lead to recurrence, which is associated with increased inflammation, hyperpigmentation, and risk of a potentially lethal generalized bullous FDE (GBFDE), which may resemble Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN). Distinguishing GBFDE from SJS and TEN is salient and will be stressed: GBFDE has more rapid onset in 1-24 h rather than in weeks, less or no mucosal involvement, less or no systemic involvement, and a tendency for a more favorable prognosis; however, recent experience suggests it may be just as life-threatening. This review will provide a comprehensive update and approach to diagnosis and management.

Mechanisms of Severe Cutaneous Adverse Reactions: Recent Advances

Cutaneous adverse drug reactions are unpredictable and include various different skin conditions of varying degrees of severity. The most concerning are usually referred to as severe cutaneous adverse reactions (SCARs) and include acute generalized exanthematous pustulosis (AGEP), drug reaction with eosinophilia and systemic symptoms (DRESS), also known as drug-induced hypersensitivity syndrome (DiHS) or hypersensitivity syndrome (HSS), Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). All are delayed type IV hypersensitivity reactions in which a T-cell-mediated drug-specific immune response is responsible for causing the disease. Nonetheless, specific T-cell subpopulations develop in response to certain environmental conditions and produce cytokines that orchestrate the various phenotypes. Cytotoxic T lymphocytes (CTLs), T-helper type 1 (Th1), Th2, Th17, and regulatory T cells (Treg), among other T-cell subpopulations, participate in the development of SCAR phenotypes. Cell subpopulations belonging to the innate immune system, comprising natural killer cells, innate lymphoid cells, monocytes, macrophages and dendritic cells, can also participate in shaping specific immune responses in various clinical conditions. Additionally, tissue-resident cells, including keratinocytes, can contribute to epidermal damage by secreting chemokines that attract pro-inflammatory immunocytes. The final phenotypes in each clinical entity result from the complex interactions between a variety of cell lineages, their products, soluble mediators and genetic and environmental factors. Although the pathophysiology of these reactions is not fully understood, intensive research in recent years has led to major progress in our understanding of the contribution of certain cell types and soluble mediators to the variability of SCAR phenotypes.

Drug-induced hypersensitivity syndrome (DiHS)/drug reaction with eosinophilia and systemic symptoms (DRESS): An update in 2019

The aim of this review was to provide an updated overview of drug-induced hypersensitivity syndrome (DiHS)/drug reaction with eosinophilia and systemic symptoms (DRESS). Several new insights have been made, particularly with regards to the diagnosis, pathogenesis and care of some important complications and sequelae. The indication of herpesvirus reactivations in diagnosis in the assessment of disease severity is now better specified. Nevertheless, because fatal complications and autoimmune sequelae have been under-recognized, there is a clear need to identify effective parameters for assessing disease severity and predicting prognosis of the disease in the early phase. In this regard, we have established a scoring system that can be used to monitor severity, predict prognosis and stratify the risk of developing severe complications including fatal cytomegalovirus (CMV) disease. Regulatory T cells are likely to be central to the mechanism and would represent potential targets for therapeutic approaches that can ameliorate inflammatory responses occurring at the acute phase while preventing the subsequent development of harmful outcomes, such as CMV disease and autoimmune diseases.

Applications of Immunopharmacogenomics: Predicting, Preventing, and Understanding Immune-Mediated Adverse Drug Reactions

Adverse drug reactions (ADRs) are a significant health care burden. Immune-mediated adverse drug reactions (IM-ADRs) are responsible for one-fifth of ADRs but contribute a disproportionately high amount of that burden due to their severity. Variation in human leukocyte antigen ( HLA) genes has emerged as a potential preprescription screening strategy for the prevention of previously unpredictable IM-ADRs. Immunopharmacogenomics combines the disciplines of immunogenomics and pharmacogenomics and focuses on the effects of immune-specific variation on drug disposition and IM-ADRs. In this review, we present the latest evidence for HLA associations with IM-ADRs, ongoing research into biological mechanisms of IM-ADRs, and the translation of clinical actionable biomarkers for IM-ADRs, with a focus on T cell-mediated ADRs.

An Updated Review of the Molecular Mechanisms in Drug Hypersensitivity

Drug hypersensitivity may manifest ranging from milder skin reactions (e.g., maculopapular exanthema and urticaria) to severe systemic reactions, such as anaphylaxis, drug reactions with eosinophilia and systemic symptoms (DRESS)/drug-induced hypersensitivity syndrome (DIHS), or Stevens–Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN). Current pharmacogenomic studies have made important strides in the prevention of some drug hypersensitivity through the identification of relevant genetic variants, particularly for genes encoding drug-metabolizing enzymes and human leukocyte antigens (HLAs). The associations identified by these studies are usually drug, phenotype, and ethnic specific. The drug presentation models that explain how small drug antigens might interact with HLA and T cell receptor (TCR) molecules in drug hypersensitivity include the hapten theory, the p-i concept, the altered peptide repertoire model, and the altered TCR repertoire model. The broad spectrum of clinical manifestations of drug hypersensitivity involving different drugs, as well as the various pathomechanisms involved, makes the diagnosis and management of it more challenging. This review highlights recent advances in our understanding of the predisposing factors, immune mechanisms, pathogenesis, diagnostic tools, and therapeutic approaches for drug hypersensitivity.

HLAs: Key regulators of T-cell-mediated drug hypersensitivity

Adverse drug reactions (ADR) can be broadly categorised as either on-target or off-target. On-target ADRs arise as a direct consequence of the pharmacological properties of the drug and are therefore predictable and dose-dependent. On-target ADRs comprise the majority (>80%) of ADRs, relate to the drug's interaction with its known pharmacological target and are a result of a complex interplay of genetic and ecologic factors. In contrast, off-target ADRs, including immune-mediated ADRs (IM-ADRs), are due to unintended pharmacological interactions such as inadvertent ligation of host cell receptors or non-pharmacological interactions mediated through an adaptive immune response. IM-ADRs can be classified according to the primary immune cell involved and include B-cell-mediated (Gell-Coombs type I-III reactions) and T-cell-mediated (Gell-Coombs type IV or delayed hypersensitivity) reactions. IM-ADRs mediated by T cells are associated with phenotypically distinct clinical diagnoses and can vary from a mild delayed rash to a life-threatening cutaneous, systemic or organ disease, such as Stephen Johnson syndrome/toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms and drug-induced liver disease. T-cell-mediated ADRs are strongly linked to the carriage of particular HLA risk alleles which are in the case of abacavir hypersensitivity and HLA-B*57:01 has led to translation into the clinic as a routine screening test. In this review, we will discuss the immunogenetics and pathogenesis of IM-ADRs and how HLA associations inform both pre-drug screening strategies and mechanistic understanding.

Severe Delayed Drug Reactions: Role of Genetics and Viral Infections

Adverse drug reactions (ADRs) are a significant source of patient morbidity and mortality and represent a major burden to health care systems and drug development. Up to 50% of such reactions are preventable. Although many ADRs can be predicted based on the on-target pharmacologic activity, ADRs arising from drug interactions with off-target receptors are recognized. Off-target ADRs include the immune-mediated ADRs (IM-ADRs) and pharmacologic drug effects. In this review, we discuss what is known about the immunogenetics and pathogenesis of IM-ADRs and the hypothesized role of heterologous immunity in the development of IM-ADRs.

Severe Delayed Cutaneous and Systemic Reactions to Drugs: A Global Perspective on the Science and Art of Current Practice

Most immune-mediated adverse drug reactions (IM-ADRs) involve the skin, and many have additional systemic features. Severe cutaneous adverse drug reactions (SCARs) are an uncommon, potentially life-threatening, and challenging subgroup of IM-ADRs with diverse clinical phenotypes, mechanisms, and offending drugs. T-cell-mediated immunopathology is central to these severe delayed reactions, but effector cells and cytokines differ by clinical phenotype. Strong HLA-gene associations have been elucidated for specific drug-SCAR IM-ADRs such as Stevens-Johnson syndrome/toxic epidermal necrolysis, although the mechanisms by which carriage of a specific HLA allele is necessary but not sufficient for the development of many IM-ADRs is still being defined. SCAR management is complicated by substantial short- and long-term morbidity/mortality and the potential need to treat ongoing comorbid disease with related medications. Multidisciplinary specialist teams at experienced units should care for patients. In the setting of SCAR, patient outcomes as well as preventive, diagnostic, treatment, and management approaches are often not generalizable, but rather context specific, driven by population HLA-genetics, the pharmacology and genetic risk factors of the implicated drug, severity of underlying comorbid disease necessitating ongoing treatments, and cost considerations. In this review, we update the basic and clinical science of SCAR diagnosis and management.

Emerging Skin T-Cell Functions in Response to Environmental Insults

Skin is the primary barrier between the body and the outside world, functioning not only as a physical barrier, but also as an immunologic first line of defense. A large number of T cells populate the skin. This review highlights the ability of these cutaneous T cells to regulate skin-specific environmental threats, including microbes, injuries, solar UV radiation, and allergens. Since much of this knowledge has been advanced from murine studies, we focus our review on how the mouse state has informed the human state, emphasizing the key parallels and differences.

Adverse cutaneous drug eruptions: current understanding

Adverse cutaneous drug reactions are recognized as being major health problems worldwide causing considerable costs for health care systems. Most adverse cutaneous drug reactions follow a benign course; however, up to 2% of all adverse cutaneous drug eruptions are severe and life-threatening. These include acute generalized exanthematous pustulosis (AGEP), drug reaction with eosinophilia and systemic symptoms (DRESS), Stevens-Johnson syndrome (SJS), and toxic epidermal necrolysis (TEN). Physicians should be aware of specific red flags to rapidly identify these severe cutaneous drug eruptions and initiate appropriate treatment. Besides significant progress in clinical classification and treatment, recent studies have greatly enhanced our understanding in the pathophysiology of adverse cutaneous drug reactions. Genetic susceptibilities to certain drugs have been identified in SJS/TEN patients, viral reactivation in DRESS has been elucidated, and the discovery of tissue resident memory T cells helps to better understand the recurrent site-specific inflammation in patients with fixed drug eruption.

Allopurinol hypersensitivity: investigating the cause and minimizing the risk

Allopurinol is the most commonly prescribed urate-lowering therapy for the management of gout. Serious adverse reactions associated with allopurinol, while rare, are feared owing to the high mortality. Such reactions can manifest as a rash combined with eosinophilia, leukocytosis, fever, hepatitis and progressive kidney failure. Risk factors for allopurinol-related severe adverse reactions include the recent introduction of allopurinol, the presence of the HLA-B(*)58:01 allele, and factors that influence the drug concentration. The interactions between allopurinol, its metabolite, oxypurinol, and T cells have been studied, and evidence exists that the presence of the HLA-B(*)58:01 allele and a high concentration of oxypurinol function synergistically to increase the number of potentially immunogenic-peptide-oxypurinol-HLA-B(*)58:01 complexes on the cell surface, thereby increasing the risk of T-cell sensitization and a subsequent adverse reaction. This Review will discuss the above issues and place this in the clinical context of reducing the risk of serious adverse reactions.

Pathogenesis and diagnosis of delayed-type drug hypersensitivity reactions, from bedside to bench and back

Drug hypersensitivity reactions (DHR) have been present since the advent of drugs. In particular T-cell mediated delayed-type hypersensitivity reactions represent a heterogeneous clinical entity with a diverse pathogenesis and result in a considerable burden of morbidity and mortality not only driven by the reactions themselves but also by the use of alternatives which are sometimes less effective or even more dangerous. Diagnostic procedures rely on clinical history, skin testing and potential provocation testing, whereas validated in vitro diagnostic procedures are still lacking for most of them. Recent work in the field of pharmacogenomics combined with basic scientific research has provided insights in the pathogenesis of abacavir and carbamazepine hypersensitivities linked with certain human leucocyte antigen risk alleles. Nevertheless, important scientific questions on how other DHR arise and how host-drug interactions occur, remain unanswered. Recent work indicates an intricate relation between host, drug and pathogens in severe cutaneous and systemic reactions and provides more insights in the role of regulatory T-cells and viral reactivation in these reactions. In this review we focus on type IV delayed-type DHR, and address recent advances in the pathogenesis, pharmacogenomics, and diagnosis of these reactions with an emphasis on the understandings arising from basic research.

Drug-Induced Hypersensitivity Syndrome Followed by Subacute Thyroiditis

Drug-induced hypersensitivity syndrome (DIHS) is a severe multiorgan system adverse drug reaction with reactivation of human herpesviruses (HHVs) such as HHV-6, HHV-7, cytomegalovirus (CMV) and Epstein-Barr virus. Various complications, including autoimmune diseases, sometimes appear during the course of DIHS. We report a case of salazosulfapyridine-induced DIHS associated with HHV-6 reactivation. Two and a half months after the onset of DIHS, subacute thyroiditis occurred, possibly associated with CMV reactivation. Prednisolone (20 mg/day) was effective for subacute thyroiditis. Long-term follow-up is needed in patients with DIHS because of the possible onset of autoimmune diseases.

Liver injury in patients with DRESS: A clinical study of 72 cases

BACKGROUND

Drug reaction with eosinophilia and systemic symptoms (DRESS) is a syndrome involving multiple systems. Liver injury is the most common visceral manifestation.

OBJECTIVE

The purpose of this study was to investigate the types of liver injury and factors associated with DRESS.

METHODS

A retrospective cohort study was conducted in Taiwan using a DRESS database compiled from December 2000 to March 2013.

RESULTS

Seventy-two cases were included in this study. Among them, 62 (86.1%) cases involved liver injury, 6 of which (9.7%) were liver injury before skin presentation. The distribution of liver injury patterns at initial presentation was 23 cholestatic type (37.1%), 17 mixed type (27.4%), and 12 hepatocellular type (19.4%). Patients with hepatocellular-type injuries were younger, with a median age of 31.5 (P = .044). Individuals with liver function results more than 10 times the upper limit were more likely to have fever (P = .026), took more time to recover, and had fewer eosinophils in the dermis (P = .002).

LIMITATIONS

The study was a retrospective cohort study with limited cases.

CONCLUSIONS

Liver injury is common in DRESS and frequently associated with atypical lymphocytosis. The cholestatic type is the most common type. Patients with cholestatic-type injuries were older and more frequently had interface changes in skin pathology.