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Background The diagnostic approach for beta-lactam (BL) drug hypersensitivity reactions (DHR) is based on the history, clinical signs, skin tests (ST), in vitro tests, and drug provocation tests (DPT). The aim of this study was to assess the performance of an allergy workup with ST in a real-world use. Methods In this cross-sectional study the rate of positive ST in subjects with suspected DHR to penicillins and cephalosporins was investigated. Of special interest were correlations of ST positivity: 1) to the time intervals between index reaction and the allergic work-up, 2) time interval from drug exposure to the onset of signs, 3) pattern of manifestation in delayed DHR and involvement of test area in the index reaction, and 4) potential advantage of patch testing in delayed DHR. Results 175 patients were included between January 2018 and April 2019 (63.4% female), 45 (25.7%) with immediate DHR manifestation and 130 with delayed DHR manifestation (74.3%). A total of 44 patients (25.1%) had a positive ST (immediate DHR 37.8% versus 20.0% in delayed DHR). ST positivity decreased in both groups after 3 years from 47.8% [95%CI 29.2–67] to 23.5% [95%CI 9.6–47.3] in immediate DHR and 23.0% [95%CI 15-4-32.9] to 12.9% [95%CI 5.1–28.9] in delayed DHR. The proportion of positive ST was higher in patients with more severe forms of delayed DHR, and in subjects with a shorter latency period of onset of symptoms after drug exposure: 0-3d: 29.5% [95%CI 19.6–41.9] vs. >3d: 11.6% [95%CI 6.0–21.2]). No sensitization was shown in delayed urticaria or angioedema. ST done outside the skin area involved during the index reaction were negative in all cases (0/38 vs. 26/84 in cases with involved area). The combination of patch test and intradermal test (IDT) revealed an additional positive result in 2/77 cases. Additional in vitro testing reduced the proportion of negative test results to 72%. Conclusion In most patients with negative test results, we could not clarify the cause of the BL-associated adverse events even with further investigations (including DPT). How to prevent new drug-induced adverse events in such patients has hardly been investigated yet. Corresponding cohort studies could improve the data situation.

Human leukocyte antigen (HLA) encoded by the HLA gene is an important modulator for immune responses and drug hypersensitivity reactions as well. Genetic polymorphisms of HLA vary widely at population level and are responsible for developing severe cutaneous adverse drug reactions (SCARs) such as Stevens–Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), drug reaction with eosinophilia and systemic symptoms (DRESS), maculopapular exanthema (MPE). The associations of different HLA alleles with the risk of drug induced SJS/TEN, DRESS and MPE are strongly supportive for clinical considerations. Prescribing guidelines generated by different national and international working groups for translation of HLA pharmacogenetics into clinical practice are underway and functional in many countries, including Thailand. Cutting edge genomic technologies may accelerate wider adoption of HLA screening in routine clinical settings. There are great opportunities and several challenges as well for effective implementation of HLA genotyping globally in routine clinical practice for the prevention of drug induced SCARs substantially, enforcing precision medicine initiatives.

Nonimmediate drug hypersensitivity reactions (niDHRs) range from mild-type maculopapular exanthema (MPE) to severe type Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) with unentirely clarified pathogenesis. This study sought to explore whether complement components participated in niDHRs. The participants comprised of three groups as follows: MPE (n = 65), SJS/TEN (n = 13, contains 7 SJS, 2 SJS-TEN overlap and 4 TEN), and equal healthy controls (n = 78). Skin pathological changes were confirmed by hematoxylin and eosin staining. The mRNA and protein levels of complement components were assessed. In the MPE group, there were no alterations in complement components at the protein and mRNA levels found except for a decrease in factor H mRNA. In the SJS/TEN group, up-regulated levels of C3aR and C5aR mRNA and down-regulated factor H mRNA levels in blood were noted. A lower plasma protein level of C3, Factor H and a higher level of C3a, C5, C5a, C5b-9, Factor B (p

To characterize human leukocyte antigen (HLA) loci as risk factors in aromatic antiepileptic drug-induced maculopapular exanthema (AED-MPE). A case-control study was performed to investigate HLA loci involved in AED-MPE in a southern Han Chinese population. Between January 2007 and June 2019, 267 patients with carbamazepine (CBZ), oxcarbazepine (OXC), or lamotrigine (LTG) associated MPE and 387 matched drug-tolerant controls from six centers were enrolled. HLA-A/B/C/DRB1 genotypes were determined using sequence-based typing. Potential risk alleles were validated by meta-analysis using data from different populations and in silico analysis of protein-drug interactions. HLA-DRB1*04:06 was significantly associated with OXC-MPE (p = 0.002, pc = 0.04). HLA-B*38:02 was associated with CBZ-MPE (p = 0.03). When pooled, HLA-A*24:02, HLA-A*30:01, and HLA-B*35:01 additionally revealed significant association with AED-MPE. Logistic regression analysis showed a multiplicative interaction between HLA-A*24:02 and HLA-B*38:02 in CBZ-MPE. Meta-analysis of data from different populations revealed that HLA-24*:02 and HLA-A*30:01 were associated with AED-MPE (p = 0.02 and p = 0.04, respectively). In silico analysis of protein-drug interaction demonstrated that HLA-A*24:02 and HLA-A*30:01 had higher affinities with the three aromatic AEDs than the risk-free HLA-A allele. HLA-DRB1*04:06 showed relatively specific high affinity with S-monohydroxy derivative of OXC. HLA-DRB1*04:06 is a specific risk allele for OXC-induced MPE in the Southern Han Chinese. HLA-A*24:02, possibly HLA-A*30:01, are common risk factors for AED-MPE. The multiplicative risk potential between HLA-A*24:02 and HLA-B*38:02 suggests that patients with two risk alleles are at greater risk than those with one risk allele. Inclusion of these HLA alleles in pre-treatment screening would help estimating the risk of AED-MPE.

The immunomodulatory effects of regulatory T cells (Tregs) and co-signaling receptors have gained much attention, as they help balance immunogenic and immunotolerant responses that may be disrupted in autoimmune and infectious diseases. Drug hypersensitivity has a myriad of manifestations, which ranges from the mild maculopapular exanthema to the severe Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug reaction with eosinophilia and systemic symptoms/drug-induced hypersensitivity syndrome (DRESS/DIHS). While studies have identified high-risk human leukocyte antigen (HLA) allotypes, the presence of the HLA allotype at risk is not sufficient to elicit drug hypersensitivity. Recent studies have suggested that insufficient regulation by Tregs may play a role in severe hypersensitivity reactions. Furthermore, immune checkpoint inhibitors, such as anti-CTLA-4 or anti-PD-1, in cancer treatment also induce hypersensitivity reactions including SJS/TEN and DRESS/DIHS. Taken together, mechanisms involving both Tregs as well as coinhibitory and costimulatory receptors may be crucial in the pathogenesis of drug hypersensitivity. In this review, we summarize the currently implicated roles of co-signaling receptors and Tregs in delayed-type drug hypersensitivity in the hope of identifying potential pharmacologic targets.

Background Antiepileptic drugs (AEDs) can cause hypersensitivity reactions in children. These reactions are mainly cutaneous, self-limiting, and benign, but life-threatening severe cutaneous adverse reactions can occur. Infections can lead to skin eruptions and mimic drug hypersensitivity reactions, if a drug is taken at the same time. The aims of our study were to confirm or rule out the diagnosis of hypersensitivity reactions to AEDs in children and to detect an infection which mimics these reactions. Methods A prospective survey was conducted in a group of 100 children with histories of hypersensitivity reactions to AEDs by performing patch tests, delayed-reading intradermal test, and, in case of negative results, challenge test. In all children, a study was performed to detect infections by viruses or Mycoplasma pneumoniae. Results Maculopapular exanthema and delayed-appearing urticaria were the most reported hypersensitivity reactions to AEDs. Sixty-six (66%) of 100 children had confirmed hypersensitivity reactions to AEDs. Fifty-nine children had positive patch test. No children had positive challenge tests. The most common AEDs causing hypersensitivity reactions were carbamazepine (45.4%) and lamotrigine (43.6%). Thirty-two children had positive tests for viruses or M pneumoniae, and nine of them had also a positive allergy work-up. Conclusion Considering that there are no specific tests to distinguish between a viral infection and hypersensitivity reactions to AEDs in the acute phase, a diagnostic work-up should be performed in all children with suspected hypersensitivity reactions to AEDs, as well as infectious agent study, to remove a false label of hypersensitivity.

Purpose of review The purpose of this review is to examine in detail the new advances in the pathomechanisms and diagnosis of immediate and nonimmediate hypersensitivity reactions to quinolones, as well as analyze cross-reactivity among different quinolones. Recent findings Hypersensitivity reactions to quinolones, especially anaphylactic reactions, have become more common in the past decade. This phenomenon could be related to their increased consumption. Although attempts have been made to standardize skin testing, the diagnosis of immediate hypersensitivity reactions to quinolones is mainly based on drug provocation. Some in-vitro, radioimmunoassay and basophil activation tests have also been used for diagnostic purposes, with results indicating that they could be complementary to in-vivo tests. Cross-reactivity seems to exist between first and second-generation quinolones, with lower levels with the third and fourth generations. However, no general rules exist for predicting cross-reactivity and it needs to be analyzed patient by patient. Nonimmediate hypersensitivity reactions also exist, especially maculopapular exanthema and fixed drug eruptions, and a T-cell mechanism has been demonstrated. Summary Over the past decade the number of hypersensitivity reactions to quinolones has increased. These reactions can be severe and diagnosis difficult to confirm. Although new in-vitro tests hold promise, drug provocation testing remains the most frequently used and reliable diagnostic method.

The initial symptoms of an HIV-1 infection were observed in four patients. The following were characteristic for the acute primary phase: (a) initial maculopapular exanthema, especially of the trunk, with occasional transition into a papulovesical appearance; (b) involvement of the oral mucosa, often of aphthous character; and (c) general malaise with fever and lymphadenopathy. The observed cutaneous changes had, on one hand, features of a Coxsackie or mononucleosis exanthema, on the other of secondary syphilis. In three patients seroconversion occurred within 2-6 weeks, the fourth failed to return for follow-up. The listed acute primary symptoms can be used as the earliest indicators of an HIV-1 infection having occurred.

Adverse drug reactions (ADRs) place a large economic strain on our health care system and prevent the use of key medications by many individuals. A subset of ADRs show evidence of mediation by the human leukocyte antigen (HLA) molecules, and numerous associations between specific ADRs and particular HLA alleles or subgroups have been identified. Here we discuss the current models for interaction of small molecule drugs with the HLA and the supporting evidence in the context of antigen-processing and presentation.

Beta-lactam antibiotics (BLs) are the most frequent cause of hypersensitivity reactions mediated by specific immunological mechanisms, with two main types, IgE reactions or T-cell-dependent responses. From a practical point of view, these reactions can be classified into immediate, for those appearing within 1 h after drug intake, and non-immediate, for those appearing at least 1 h after and usually within 24 h of BL administration. The clinical symptoms differ according to this classification. Urticaria and anaphylaxis are the most frequently recorded symptoms in immediate reactions and maculopapular exanthema and delayed urticaria in non-immediate reactions. Although the exact diagnostic approach differs depending on the underlying mechanism, it is based on the performance of skin testing, laboratory tests, and drug provocation tests.

Results Ninety patients were evaluated, 54 male, with a median age of 6 years. Personal history of atopy was reported in 65 and previous DHR in 9. Cutaneous manifestations were observed in 86 – urticaria and/or angioedema in 71 and macular or maculopapular exanthema in 15. Other symptoms reported were: respiratory (25), gastrointestinal (8), cardiovascular (5). The interval between dose and reaction was less than 1 hour in 38 subjects. Mild reaction was observed in 32 patients and moderate in 55. Fever and/or viral infection were present in 61 patients during or just before the reaction. The majority of subjects were treated in emergency units (79). More than one drug was suspected as a trigger in 50 children (NSAIDs in 50%, beta-lactam antibiotics in 31% and other antibiotics in 8.5%). Sixteen skin tests (prick and intradermal) were performed and were all negative but one with amoxicilin. Drug provocation tests were positive in 4 of 51 tests NSAIDs 29 (4 positive), beta-lactam antibiotics 20 and others 4. Sixty-one reactions were possible or probable related with the suspected drug, but in 25 this relation was unlikely.

Background Immune-mediated cutaneous adverse drug reactions (CADR) present under different clinical patterns, some different from the main phenotypes of CADR. Our objective is to characterize manifestations and culprit drugs in CADR that required hospitalization, particularly exanthema associated with few systemic symptoms without fulfilling the European DRESS criteria (MP/DR).