Delayed cutaneous manifestations of drug hypersensitivity

Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS): Focus on the Pathophysiological and Diagnostic Role of Viruses

Drug reaction with eosinophilia and systemic symptoms (DRESS) is a heterogeneous, multiorgan and potentially life-threatening drug-hypersensitivity reaction (DHR) that occurs several days or weeks after drug initiation or discontinuation. DHRs constitute an emerging issue for public health, due to population aging, growing multi-organ morbidity, and subsequent enhanced drug prescriptions. DRESS has more consistently been associated with anticonvulsants, allopurinol and antibiotics, such as sulphonamides and vancomycin, although new drugs are increasingly reported as culprit agents. Reactivation of latent infectious agents such as viruses (especially Herpesviridae) plays a key role in prompting and sustaining aberrant T-cell and eosinophil responses to drugs and pathogens, ultimately causing organ damage. However, the boundaries of the impact of viral agents in the pathophysiology of DRESS are still ill-defined. Along with growing awareness of the multifaceted aspects of immune perturbation caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) during the ongoing SARS-CoV-2-related disease (COVID-19) pandemic, novel interest has been sparked towards DRESS and the potential interactions among antiviral and anti-drug inflammatory responses. In this review, we summarised the most recent evidence on pathophysiological mechanisms, diagnostic approaches, and clinical management of DRESS with the aim of increasing awareness on this syndrome and possibly suggesting clues for future research in this field.

Patch testing versus interferon-gamma release assay in evaluation of drug eruptions

Delayed-onset T-cell-mediated cutaneous adverse drug reactions are an uncommon but potentially serious result of medication exposures. Identification of culprit medications is crucial, but clinical diagnosis is often difficult. Patch tests and interferon-gamma release assays (IFNγ-RA) were previously reported as potentially useful ancillary tests, while rechallenges remain the reference standard test. We compared the number of positive test results with patch testing and IFNγ-RA for drugs implicated as possible causes of cutaneous reactions. Fifty-one patients with a suspected cutaneous drug eruption underwent patch testing and IFNγ-RA for suspected drugs. Participants were followed up at least 9 months after the onset of the rash with results compared with the clinical diagnosis. Forty-two patients presented with morbilliform/eczematous eruptions; five were diagnosed with fixed drug eruption (FDE) and four with erythema multiforme. None had positive patch testing to the drugs tested. A total of 8/51 (15.6%) patients had positive reaction by the IFNγ-RA, and an additional 11 (21.6%) patients had borderline results. Positive or borderline results were more likely in patients with FDE (80%) than morbilliform/eczematous eruptions (30.9%) or erythema multiforme (25%). Our study emphasizes the necessity of additional effective ancillary tests in the evaluation of drug eruptions and supports the use of IFNγ-RA for drug testing as a tool for identifying medications associated with cutaneous drug eruptions.

Tackling the Patient with Multiple Drug "Allergies": Multiple Drug Intolerance Syndrome

As populations age, the prevalence of reported drug "allergy" increases, often leading to suboptimal care and increased morbidity because of unnecessary avoidance of safe and effective medications. Evaluation by a drug allergy specialist is often warranted when a patient has more than 2 unrelated drug "allergies" listed in the medical record. In this commentary, we clarify and propose standard terminology to use when evaluating patients with multiple drug allergy labels including and more specifically when diagnosing multiple drug intolerance syndrome and the much rarer multiple drug hypersensitivity syndrome. We review epidemiology and key features of multiple drug intolerance syndrome and multiple drug hypersensitivity syndrome. We summarize the methodologic and practical diagnostic workup and management of individuals with MDIS to assist with the accurate delabeling of drug "allergies" in the electronic health record.

Neutrophil-to-lymphocyte ratio is a prognostic predictor in emergency department patients with cutaneous adverse drug reaction

OBJECTIVE

We aimed to evaluate the prognostic value of neutrophil-to-lymphocyte ratio (NLR) in emergency department (ED) patients with cutaneous adverse drug reactions to identify the severe patients at an early stage.

METHODS

In this retrospective study, patients aged 18 and over who admitted to the ED of a university hospital with the diagnosis of cutaneous adverse drug reaction were included. For included patients, clinical findings and ED admission complete blood count results were recorded. The primary outcome was hospitalization and the secondary outcome was the type of drug reaction.

RESULTS

A total of 135 patients were included in the study. The median age of patients was 50 (36-64) years. There was no significant difference between the patients hospitalized and discharged from the ED in terms of age and gender (p = 0.340 and p = 0.762, respectively). There was no significant difference between hospitalized and discharged patients in terms of complete blood count parameters (p > 0.05, for all). The median NLR of hospitalized patients was significantly higher than that of patients discharged from the ED (6.13 vs. 3.69, p = 0.006). The median NLR of the patients with erythema multiform/Steven Johnson syndrome/toxic epidermal necrosis was significantly higher than the NLR of the patients with maculopapular and fixed drug eruptions (p = 0.022 and p = 0.015, respectively). The area under the curve value of NLR in predicting hospitalization was 0.640 (0.546-0.734). For 8.4 of NLR cutoff value, specificity was 83.9%.

CONCLUSION

NLR is a useful and simple prognostic parameter as an indicator of systemic inflammatory involvement in ED patients with cutaneous adverse drug reactions. NLR is a useful parameter for deciding which patient will be admitted to the hospital in that patient group.

Prevalence of Antibiotic Allergy Labels in a Tertiary Referral Center in Belgium

BACKGROUND

Antibiotic (AB) allergies are among the most frequently occurring adverse drug reactions. In US literature, AB allergy labels (AAL) are reported in 10% to 15% of patients' charts; however, large-scale European analyses are scarce.

OBJECTIVES

To retrospectively assess the prevalence of AAL in a tertiary referral hospital in Belgium between 2010 and 2018.

METHODS

Patients who consulted and/or were hospitalized during the study period, who had been labeled with an AB allergy, were selected for further analysis.

RESULTS

Of 1,009,598 unique patients (outpatients, n = 736,469; inpatients, n = 273,129), 28,147 patients (3%) were registered with 1 or more AAL, being 1% of outpatients (n = 9562) and 7% of inpatients (n = 18,585). Women were more likely to carry an AAL (68%) compared with men (32%, P < .001). In patients with an AAL, 9% had multiple labels and 5% had labels for multiple AB classes. Most frequently, beta-lactams were involved (84% of AAL), followed by quinolones (7%) and sulfonamides and macrolides (both 3%). Moreover, 88% of the reactions were self-reported, mostly being an unspecified rash (53%), whereas only 3% were considered confirmed AAL.

CONCLUSION

With an overall prevalence of 3%, the burden of AAL is less in our Western European center compared with US reports. However, this prevalence most likely still represents an overestimation of genuine AB allergic patients because most labels lack confirmation and/or specifications. Our work indicates that knowledge of the local epidemiology of AAL is necessary to estimate the impact of better allergy labeling and delabeling strategies.

Global implementation of the world health organization's International Classification of Diseases (ICD)-11: The allergic and hypersensitivity conditions model

The International Classification of Diseases (ICD) provides a common language for use worldwide as a diagnostic and classification tool for epidemiology, clinical purposes and health management. Since its first edition, the ICD has maintained a framework distributing conditions according to topography, with the result that some complex conditions, such as allergies and hypersensitivity disorders (A/H) including anaphylaxis, have been poorly represented. The change in hierarchy in ICD-11 permitted the construction of the pioneer section addressed to A/H, which may result in more accurate mortality and morbidity statistics, including more accurate accounting for mortality due to anaphylaxis, strengthen classification, terminology and definitions. The ICD-11 was presented and adopted by the 72nd World Health Assembly in May 2019, and the implementation is ongoing worldwide. We here present the outcomes from an online survey undertaken to reach out the allergy community worldwide in order to peer review the terminology, classification and definitions of A/H introduced into ICD-11 and to support their global implementation. Data are presented here for 406 respondents from 74 countries. All of the subsections of the new A/H section of the ICD-11 had been considered with good accuracy by the majority of respondents. We believe that, in addition to help during the implementation phase, all the comments provided will help to improve the A/H classification and to increase awareness by different disciplines of what actions are needed to ensure more accurate epidemiological data and better clinical management of A/H patients.

Characteristics of cutaneous adverse drug reactions caused by triple-combination drug therapy used for Helicobacter pylori eradication

Cutaneous adverse drug reactions (cADR) should be appropriately managed in drug administration. LANSAP® , Rabecure® and VONOSAP® are currently used for Helicobacter pylori eradication therapy. Here, we examined the characteristics of cADR caused by these drugs using data from the Pharmaceuticals and Medical Devices Agency (PMDA). Periods subject to analyses were set according to the year of release of these drugs: (i) from 2008 to 2017 for LANSAP; (ii) from 2014 to 2017 for Rabecure; and (iii) 2017 for VONOSAP. Among all cADR reported to the PMDA, those attributed to LANSAP, Rabecure and VONOSAP accounted for 2.3%, 1.0% and 3.6% of cases, respectively. cADR occurred in patients aged in their 20s or older, with the oldest patients aged in their 60s. Numbers of male and female patients were 28 and 70 for LANSAP, eight and 14 for Rabecure and three and 16 for VONOSAP, respectively. Statistical analyses revealed significant sex differences for LANSAP (P = 0.022) and VONOSAP (P = 0.012), but not for Rabecure (P = 0.729). LANSAP, Rabecure or VONOSAP caused erythema multiforme in the largest population of patients and Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) in three patients. Ratios of SJS/TEN were 0.0-5.3% for LANSAP, Rabecure or VONOSAP, but 11.5-44.8% for the corresponding single constituent drugs other than vonoprazan. In conclusion, female sex appears to represent a risk factor for cADR attributed to H. pylori eradication therapy using LANSAP or VONOSAP, although H. pylori eradication therapy without these drugs rarely causes severe cADR.

A Critical Evaluation of Safety Signal Analysis Using Algorithmic Standardised MedDRA Queries

INTRODUCTION

Algorithmic Standardised MedDRA^® Queries (aSMQs) are increasingly used to enhance the efficiency of safety signal detection. The manner that aSMQs affect capture of potential safety cases is unclear.

OBJECTIVES

Our objective was to characterise the performance of aSMQs with respect to their potential for double counting, the likelihood of events in aSMQ positive cases being clinically related, how frequently terms are used for algorithmically positive cases, and the face validity of positive cases based on the drug inducing events. We were also interested in what effect requiring symptoms to overlap temporally would have on performance.

METHODS

We reviewed adverse event (AE) datasets of New Drug Applications and Biological License Applications and compiled a database including preferred terms and corresponding SMQs, SMQ term categories, AE start day, AE duration, drug name, and Anatomical Therapeutic Chemical class. Two reviewers independently determined if the algorithm was met and, if so, whether the broad terms overlapped temporally.

RESULTS

A total of 107 marketing applications were reviewed, including 103,928 patients and 277,430 AEs. Use of algorithms condensed the number of AEs to between 5 and 8% and the incidence to about 1.5% relative to when the SMQs are used without the algorithm. Certain aSMQs exhibited a potential for overcounting. Requiring symptoms to temporally overlap helped to eliminate irrelevant cases.

CONCLUSIONS

Our findings demonstrate that algorithmic and temporal assessment increased specificity of case retrieval, though the reduction in the number of terms or incidence seemed excessive for certain aSMQs. Evaluating the day of AE onset and duration improve specificity through identification of outlying events. Identification of drug classes known to cause the aSMQ's clinical condition provides face validity for this tool, yet detection of cases associated with novel classes may provide new understanding of these disorders. Improvements in some of the SMQ term lists may improve the performance of SMQs in general.

An EAACI task force report: recognising the potential of the primary care physician in the diagnosis and management of drug hypersensitivity

Adverse drug reactions include drug hypersensitivity reactions (DHRs), which can be immunologically mediated (allergy) or non-immunologically mediated. The high number of DHRs that are unconfirmed and often self-reported is a frequent problem in daily clinical practice, with considerable impact on future prescription choices and patient health. It is important to distinguish between hypersensitivity and non-hypersensitivity reactions by adopting a structured diagnostic approach to confirm or discard the suspected drug, not only to avoid life-threatening reactions, but also to reduce the frequent over-diagnosis of DHRs. Primary care physicians are often the first point of contact for the sufferer of a reaction, as such they have a key role in deciding whether to discard the diagnosis or send the patient for further investigation. In this review, we highlight the importance of diagnosing DHRs, analysing in detail the role of primary care physicians. We describe the common patterns of DHRs and signs of its progression, as well as the indications and contraindications for referring the patient to an allergist. The diagnostic process is described and the possible tests are discussed, which often depend on the drug involved and the type of DHR suspected. We also describe recommendations regarding the avoidance of medication suspected to have caused the reaction and the use of alternatives.

Eosinophils from Physiology to Disease: A Comprehensive Review

Despite being the second least represented granulocyte subpopulation in the circulating blood, eosinophils are receiving a growing interest from the scientific community, due to their complex pathophysiological role in a broad range of local and systemic inflammatory diseases as well as in cancer and thrombosis. Eosinophils are crucial for the control of parasitic infections, but increasing evidence suggests that they are also involved in vital defensive tasks against bacterial and viral pathogens including HIV. On the other side of the coin, eosinophil potential to provide a strong defensive response against invading microbes through the release of a large array of compounds can prove toxic to the host tissues and dysregulate haemostasis. Increasing knowledge of eosinophil biological behaviour is leading to major changes in established paradigms for the classification and diagnosis of several allergic and autoimmune diseases and has paved the way to a "golden age" of eosinophil-targeted agents. In this review, we provide a comprehensive update on the pathophysiological role of eosinophils in host defence, inflammation, and cancer and discuss potential clinical implications in light of recent therapeutic advances.

Eosinophilic Drug Allergy

While peripheral or tissue eosinophilia may certainly characterize drug eruptions, this feature is hardly pathognomonic for a medication-induced etiology. While delayed drug hypersensitivity reactions with prominent eosinophilic recruitment have been typically classified as type IVb reactions, their pathophysiology is now known to be more complex. Eosinophilic drug reactions have a diversity of presentations and may be benign and self-limited to severe and life-threatening. The extent of clinical involvement is also heterogeneous, ranging from isolated peripheral eosinophilia or single organ involvement (most often the skin and lung) to systemic disease affecting multiple organs, classically exemplified by drug-reaction with eosinophilia and systemic symptoms (DRESS). The spectrum of implicated medications in the causation of DRESS is ever expanding, and multiple factors including drug metabolites, specific HLA alleles, herpes viruses, and immune system activation have been implicated in pathogenesis. Due to this complex interplay of various factors, diagnostic workup in terms of skin and laboratory testing has not been validated. Similarly, the lack of controlled trials limits treatment options. This review also describes other localized as well as systemic manifestations of eosinophilic disease induced by various medication classes, including their individual pathophysiology, diagnosis, and management. Given the multitude of clinical patterns associated with eosinophilic drug allergy, the diagnosis can be challenging. Considerable deficits in our knowledge of these presentations remain, but the potential for severe reactions should be borne in mind in order to facilitate diagnosis and institute appropriate management.

Significant HLA class I type associations with aromatic antiepileptic drug (AED)-induced SJS/TEN are different from those found for the same AED-induced DRESS in the Spanish population

Aromatic antiepileptic drugs (AEDs) are among the drugs most frequently involved in severe cutaneous adverse reactions (SCARs), such as Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug reactions with eosinophilia and systemic symptoms (DRESS). This study investigated the associations between the genetic polymorphisms of HLA class-I and AED-induced SCARs in the Spanish population. HLA class-I genotypes were determined in AED (phenytoin[PHT],lamotrigine[LTG],carbamazepine[CBZ],phenobarbital[PB])-induced SJS/TEN (n=15) or DRESS (n=12) cases included in the Spanish SCAR registry, PIELenRed. There were 3 control groups: (A)tolerant to a single AED, (B)tolerant to any AED, and (C)Spanish population controls. For SJS/TEN, concomitant HLA-A*02:01/Cw15:02 alleles were significantly associated with PHT-cases compared to control groups B and C [(B)odds ratio(OR):14.75, p=0.009;(C)OR:27.50, p<0.001], and were close to significance with respect to control group A (p=0.060). The genotype frequency of the HLA-B*38:01 was significantly associated with PHT-LTG-cases compared with the 3 groups of controls [(A)OR:12.86, p=0.012;(B)OR:13.81; p=0.002;(C)OR:14.35, p<0.001], and with LTG-cases [(A)OR:147.00, p=0.001;(B)OR:115.00, p<0.001;(C)OR:124.70, p<0.001]. We found the HLA-B*15:02 allele in a Spanish Romani patient with a CBZ-case. The HLA-A*11:01 was significantly associated with CBZ-cases [(A)OR:63.89, p=0.002;(B)OR:36.33, p=0.005;(C)OR:28.29, p=0.007]. For DRESS, the HLA-A*24:02 genotype frequency was statistically significant in the PHT-LTG-cases [(A)OR:22.56, p=0.003;(B)OR:23.50. p=0.001; (C)OR:33.25, p<0.001], and in the LTG-cases [(A),OR:49.00, p=0.015;(B)OR:27.77, p=0.005; (C)OR:34.53, p=0.002]. HLA-A*31:01 was significantly associated with the CBZ-cases [(A)OR:22.00, p=0.047;(B)OR:29.50, p=0.033;(C)OR:35.14, p=0.006]. In conclusion, we identified several significant genetic risk factors for the first time in the Spanish Caucasian population: HLA-A*02:01/Cw*15:02 combination as a risk factor for PHT-induced SJS/TEN, HLA-B*38:01 for LTG- and PHT- induced SJS/TEN, HLA-A*11:01 for CBZ-induced SJS/TEN, and HLA-A*24:02 for LTG- and PHT- induced DRESS. The strong association between HLA*31:01 and CBZ-DRESS in Europeans was confirmed in this study.

Dissemination of definitions and concepts of allergic and hypersensitivity conditions

BACKGROUND

Allergy and hypersensitivity can affect people of any age and manifest with problems in a range of organ systems. Moreover, they can have a significant impact on the quality of life of patients and their families. Although once rare, there is presently an epidemic of allergic disorders with associated considerable societal consequences. Our understanding of the pathophysiology of these disorders has changed substantially over the last 20 years. In the light of these developments, the Joint Allergy Academies have made concerted efforts to ensure that these are reflected in the current definitions and concepts used in clinical allergy and to ensure these are reflected in the forthcoming International Classification of Diseases-11 (ICD-11).

OBJECTIVE

In this review, we seek to provide an update on the current definitions and concepts in relation to allergic disorders.

RESULTS

Once the new section has been built in the ICD-11 to address allergic and hypersensitivity conditions, we have been moving actions to try to support awareness by disseminating updated concepts in the field. Aligned with the ICD and the WAO philosophy of being global, this document presents fundamental and broad allergy concepts to strengthen the understanding by different health professionals worldwide, besides to support the formation of in training students.

CONCLUSION

This current review intends to be accepted and used universally by all health professionals involved in diseases' classification and coding and, therefore, contribute to improve care and outcomes in this increasing sub-section of the world's population.

Supporting the validation of the new allergic and hypersensitivity conditions section of the World Health Organization International Classification of Diseases-11

Background

The new International Classification of Diseases (ICD)-11 "Allergic and hypersensitivity conditions" section has been constructed as a result of a detailed and careful action plan based on scientific evidences for the necessity of changes and collaboration with the World Health Organization (WHO) ICD-11 revision governance. All the efforts are being acknowledged by the Joint Allergy Academies.

Objective

Considering the new classification model addressed to the allergic and hypersensitivity conditions and following the ICD WHO agenda, we believe it is the appropriate time to start supporting the validation process in collaboration with the WHO ICD governance.

Methods

We conducted a mapping of ICD-10 allergic and hypersensitivity conditions in the ICD-11 beta phase structure and categorized the conditions as fitting by "precoordination," "postcoordination," "indexed to the ICD-11 Foundation," "no code fit properly" or "no correspondence" in the ICD-11.

Results

From overall 125 ICD-10 entities spread in 6 chapters, 57.6% were able to be precoordinated, 4% postcoordinated, 12% indexed to the Foundation, 9.6% had no code fitting properly and 18.6% had no correspondence in the ICD-11 framework.

Conclusion

We have been able to demonstrate that 83.2% of the ICD-10 allergic and hypersensitivity conditions could be captured by the current ICD-11 beta draft framework. We strongly believe that our findings constitute a key step forward for a softer transition of the ICD-10 allergic and hypersensitivity conditions to the ICD-11, supporting the WHO in this process as well as strengthening the visibility of the Allergy specialty and ensuring quality management of allergic patients.

Warfarin-induced leukocytoclastic vasculitis and proteinuria

Warfarin is typically prescribed for patients with thromboembolic diseases and atrial fibrillation. In addition to the complications of bleeding, allergic skin reaction is one of its rare adverse effects. We herein report a case of a 79 year old male patient with leukocytoclastic vasculitis and proteinuria secondary to warfarin. The warfarin was discontinued and oral prednisone therapy was initiated. The cutaneous lesions and the proteinuria resolved thereafter.

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.

Lichen planus and other lichenoid dermatoses: Kids are not just little people

Lichenoid dermatoses, a group of inflammatory skin conditions with characteristic clinical and histopathologic findings, range from common to rare. Classic lichen planus typically presents as pruritic, polygonal, violaceous flat-topped papules and plaques; many variants in morphology and location also exist. Other lichenoid dermatoses share similar clinical presentations and histopathologic findings. These include lichenoid drug eruption, lichen planus-like keratosis, lichen striatus, lichen nitidus, and keratosis lichenoides chronica. Epidemiologic characteristics vary among each lichenoid disorder. While classic lichen planus is considered a disease of adults, other lichenoid dermatoses may be more common in younger populations. The literature contains an array of reports on the variations in presentation and successful management of lichen planus and lichenoid dermatoses among diverse populations. Familiarity with the characteristics of each lichenoid dermatosis, rare or common within each patient population, is key to accomplishing timely recognition and effective management.

Constructing a classification of hypersensitivity/allergic diseases for ICD-11 by crowdsourcing the allergist community

The global allergy community strongly believes that the 11th revision of the International Classification of Diseases (ICD-11) offers a unique opportunity to improve the classification and coding of hypersensitivity/allergic diseases via inclusion of a specific chapter dedicated to this disease area to facilitate epidemiological studies, as well as to evaluate the true size of the allergy epidemic. In this context, an international collaboration has decided to revise the classification of hypersensitivity/allergic diseases and to validate it for ICD-11 by crowdsourcing the allergist community. After careful comparison between ICD-10 and 11 beta phase linearization codes, we identified gaps and trade-offs allowing us to construct a classification proposal, which was sent to the European Academy of Allergy and Clinical Immunology (EAACI) sections, interest groups, executive committee as well as the World Allergy Organization (WAO), and American Academy of Allergy Asthma and Immunology (AAAAI) leaderships. The crowdsourcing process produced comments from 50 of 171 members contacted by e-mail. The classification proposal has also been discussed at face-to-face meetings with experts of EAACI sections and interest groups and presented in a number of business meetings during the 2014 EAACI annual congress in Copenhagen. As a result, a high-level complex structure of classification for hypersensitivity/allergic diseases has been constructed. The model proposed has been presented to the WHO groups in charge of the ICD revision. The international collaboration of allergy experts appreciates bilateral discussion and aims to get endorsement of their proposals for the final ICD-11.

Categorization of allergic disorders in the new World Health Organization International Classification of Diseases

BACKGROUND

Although efforts to improve the classification of hypersensitivity/allergic diseases have been made, they have not been considered a top-level category in the International Classification of Diseases (ICD)-10 and still are not in the ICD-11 beta phase linearization. ICD-10 is the most used classification system by the allergy community worldwide but it is not considered as appropriate for clinical practice. The Systematized Nomenclature of Medicine Clinical Terms (SNOMED CT) on the other hand contains a tightly integrated classification of hypersensitivity/allergic disorders based on the EAACI/WAO nomenclature and the World Health Organization (WHO) may plan to align ICD-11 with SNOMED CT so that they share a common ontological basis.

METHODS

With the aim of actively supporting the ongoing ICD-11 revision and the optimal practice of Allergology, we performed a careful comparison of ICD-10 and 11 beta phase linearization codes to identify gaps, areas of regression in allergy coding and possibly reach solutions, in collaboration with committees in charge of the ICD-11 revision.

RESULTS

We have found a significant degree of misclassification of terms in the allergy-related hierarchies. This stems not only from unclear definitions of these conditions but also the use of common names that falsely imply allergy. The lack of understanding of the immune mechanisms underlying some of the conditions contributes to the difficulty in classification.

CONCLUSIONS

More than providing data to support specific changes into the ongoing linearization, these results highlight the need for either a new chapter entitled Hypersensitivity/Allergic Disorders as in SNOMED CT or a high level structure in the Immunology chapter in order to make classification more appropriate and usable.

Antibiotic allergy

Although allergy to β-lactam and non-β-lactam antibiotics is commonly claimed, true allergy to these drugs is often absent. Reactions to antibiotics can be classified according to the interval between the last administration of the drug and the onset of symptoms, but except for immediate reactions occurring within an hour of exposure, which are almost always either IgE-mediated or due to direct stimulation of mast cells, reactions occurring later than 1 hour probably have multiple mechanisms, including being IgE-mediated or involving cell-mediated reactions. The latter are likely caused by drug-specific T lymphocytes. The diagnosis of antibiotic allergy can be difficult.

International Consensus on drug allergy

When drug reactions resembling allergy occur, they are called drug hypersensitivity reactions (DHRs) before showing the evidence of either drug-specific antibodies or T cells. DHRs may be allergic or nonallergic in nature, with drug allergies being immunologically mediated DHRs. These reactions are typically unpredictable. They can be life-threatening, may require or prolong hospitalization, and may necessitate changes in subsequent therapy. Both underdiagnosis (due to under-reporting) and overdiagnosis (due to an overuse of the term ‘allergy’) are common. A definitive diagnosis of such reactions is required in order to institute adequate treatment options and proper preventive measures. Misclassification based solely on the DHR history without further testing may affect treatment options, result in adverse consequences, and lead to the use of more-expensive or less-effective drugs, in contrast to patients who had undergone a complete drug allergy workup. Several guidelines and/or consensus documents on general or specific drug class-induced DHRs are available to support the medical decision process. The use of standardized systematic approaches for the diagnosis and management of DHRs carries the potential to improve outcomes and should thus be disseminated and implemented. Consequently, the International Collaboration in Asthma, Allergy and Immunology (iCAALL), formed by the European Academy of Allergy and Clinical Immunology (EAACI), the American Academy of Allergy, Asthma and Immunology (AAAAI), the American College of Allergy, Asthma and Immunology (ACAAI), and the World Allergy Organization (WAO), has decided to issue an International CONsensus (ICON) on drug allergy. The purpose of this document is to highlight the key messages that are common to many of the existing guidelines, while critically reviewing and commenting on any differences and deficiencies of evidence, thus providing a comprehensive reference document for the diagnosis and management of DHRs.

Induction of accelerated reactions to amoxicillin by T-cell effector mechanisms

BACKGROUND

Although allergic drug reactions have been considered to be immediate (IgE mediated) or delayed (T-cell effector mechanisms), accelerated reactions have also been defined; however, they have not been sufficiently studied.

OBJECTIVE

To study the mechanisms involved in accelerated reactions to amoxicillin.

METHODS

We monitored the response in 3 patients who had an accelerated reaction to amoxicillin. A T-cell effector response was searched after a Drug Provocation Test. Symptoms were recorded after initiation of the reaction, and sequential samples were taken at different intervals after challenge. Skin biopsy specimens were also taken, and a lymphocyte transformation test (LTT) was performed.

RESULTS

After the drug provocation test, all 3 patients had a positive response within 2 to 6 hours of drug administration, with full expression at 6 hours, requiring corticoids and antihistamine treatment. They had generalized erythema with facial angioedema but no cardiovascular or respiratory symptoms. Monitoring of the response revealed the presence in the skin of CD4 and CD8 lymphocytes with increased expression of homing and cell activation markers. Immunohistochemistry revealed a perivascular mononuclear cell infiltrate with activated CD4 and CD8 cells expressing perforin and granzyme B. No tryptase release was detected in either the affected tissue or the peripheral blood. The LTT result was positive in all 3 patients.

CONCLUSION

We found that accelerated reactions to β-lactams are mediated by effector T cells. The increase in different T-cell markers and a positive LTT result to amoxicillin, in parallel with the occurrence of symptoms after challenge, support this mechanism.

Symmetrical drug-related intertriginous and flexural exanthema (baboon syndrome) induced by amoxicillin-clavulanate

Systemic drug-related intertriginous and flexural exanthema (SDRIFE), also known as Baboon syndrome, is an uncommon, cutaneous reaction that occurs after the systemic administration of drug-related allergens. We report the case of a 5-year-old boy with SDRIFE after systemic administration of amoxicillin-clavulanate.

Drug hypersensitivity reactions targeting the skin in dogs and cats

Adverse drug reactions (ADRs) can be dose dependent or idiosyncratic. Most idiosyncratic reactions are believed to be immune-mediated; such drug hypersensitivities and allergies are unpredictable. Cutaneous reactions are the most common presentation of drug allergies. In veterinary medicine it can be difficult to assess the true prevalence of adverse drug reactions, although reports available suggest that they occur quite commonly. There are multiple theories that attempt to explain how drug allergies occur, because the pathogenesis is not yet well understood. These include the (pro)-hapten hypothesis, the Danger Theory, the pi concept, and the viral reactivation theory. Cutaneous drug allergies in veterinary medicine can have a variety of clinical manifestations, ranging from pruritus to often fatal toxic epidermal necrolysis. Diagnosis can be challenging, as the reactions are highly pleomorphic and may be mistaken for other dermatologic diseases. One must rely heavily on history and physical examination to rule out other possibilities. Dechallenge of the drug, histopathology, and other diagnostic tests can help to confirm the diagnosis. New diagnostic tools are beginning to be used, such as antibody or cellular testing, and may be used more in the future. There is much yet to learn about drug allergies, which makes future research vitally important. Treatment of drug allergies involves supportive care, and additional treatments, such as immunosuppressive medications, depend on the manifestation of the disease. Of utmost importance is to avoid the use of the incriminating drug in future treatment of the patient, as subsequent reactions can be worse, and ultimately can prove fatal.

Warfarin-induced leukocytoclastic vasculitis: a case report and review of literature

Warfarin is widely prescribed for patients with atrial fibrillation. In addition to unexpected bleeding, allergic skin reaction is one of its uncommon adverse effects. We herein report an 89-year-old man who, after taking warfarin for 4 years, suffered extensive skin eruptions. The skin biopsy disclosed leukocytoclastic vasculitis. The causal relationship between skin lesions and warfarin was confirmed after re-challenge of warfarin. A literature review revealed only 13 such cases reported from 1980 to 2011. Clinicians should be aware of this potential adverse effect of warfarin.