Fixed drug eruption: pathogenesis and diagnostic tests

Pathophysiology of drug hypersensitivity

Drug hypersensitivity reactions (DHRs) are type B adverse drug reactions (ADRs) traditionally defined as unpredictable, dose independent and not related to the drug pharmacology. DHRs, also called drug allergy if the immune system involvement is confirmed, represent around one-sixth of all ADRs and can cause major clinical problems due to their vague clinical presentation and irregular time course. Understanding the underlying pathophysiology of DHRs is very important for their diagnosis and management. Multiple layers of evidence exist pointing to the involvement of the immune system in DHRs. Recent data have led to a paradigm shift in our understanding of the exact pathophysiology of these reactions. Numerous hypotheses proposing explanation on how a low molecular weight drug molecule can elicit an immune reaction have been proposed. In addition to the classical "hapten" hypothesis, the reactive metabolite hypothesis, the pharmacological interaction with the immune system (p-i) concept, the danger/injury hypothesis and the altered peptide repertoire hypothesis have been proposed. We here introduce the inflammasome activation hypothesis and the cross-reactivity hypothesis as additional models explaining the pathophysiology of DHRs. Available data supporting these hypotheses are briefly summarized and discussed. We also introduced the cross-reactivity model, which may provide a platform to appreciate the potential role played by other factors leading to the activation of the immune system. We believe that although the drug in question could be the trigger of the reaction, the components of the immune system mediating the reaction do not act in isolation but rather are affected by the proinflammatory milieu occurring at the time of the reaction. This review attempts to summarize the available evidence to further illustrate the pathophysiology of DHRs.

Fixed Drug Eruption due to Dupilumab

Abstract is missing (Short communication)

Cefepime-Induced Generalized Fixed Drug Eruption With Morbilliform Rash

Fixed drug eruption (FDE) is a cutaneous reaction that characteristically recurs in the same locations upon re-exposure to the offending drug(s). The typical presentation of FDEs is single or multiple violaceous plaques with hyperpigmentation due to inflammation. The causative agents for FDEs include antibiotics, nonsteroidal anti-inflammatory drugs (NSAIDs), acetaminophen, barbiturates, and anticonvulsants. We present an interesting case of a generalized fixed drug eruption secondary to cefepime that resolved with the cessation of the offending drug and the institution of antihistamines and topical steroids.

Fixed drug eruption-induced balanoposthitis: a case report

Fixed Drug Eruptions (FDE) represent a distinctive type of adverse drug reaction, typically characterized by recurring, sharply demarcated skin lesions occurring at identical sites with each administration of the causative drug. A less frequent, albeit significant manifestation of FDE, is balanoposthitis, an inflammatory condition affecting the glans penis and prepuce. This rare case report explores the clinical presentation, diagnosis, and therapeutic management of FDE-induced balanoposthitis in a 34-year-old male patient who developed this condition following azithromycin administration to treat a pulmonary infection. The patient's distinctive symptoms, coupled with a medical history of similar antibiotic-induced reactions, pointed strongly towards an FDE diagnosis. Management entailed immediate discontinuation of the offending drug and initiation of symptomatic treatment, culminating in a positive therapeutic outcome. This case illuminates the potential of commonly prescribed medications, such as antibiotics, to incite balanoposthitis via FDE. It underscores the critical need for healthcare professionals to include FDE in their differential diagnosis for balanoposthitis, especially when patient exposure to high-risk medications is evident. Furthermore, the report emphasizes the pressing requirement for additional research to elucidate the pathogenesis of FDE-induced balanoposthitis and to devise effective therapeutic and preventive measures.

Neutrophilic fixed drug eruption, a histopathologic variant or an expected finding?-A report of two cases and review of the literature

Fixed drug eruption (FDE) is an adverse drug reaction characterized by recurrent circumscribed lesions at the same location upon re-exposure to the culprit medication, resulting in distinct postinflammatory hyperpigmentation. Histopathologically, FDE demonstrates a predominantly lymphocytic interface or lichenoid infiltrate with basal cell vacuolar changes and keratinocyte dyskeratosis/apoptosis. The term "neutrophilic fixed drug eruption" has been used to describe cases in which the inflammatory infiltrate is predominantly neutrophilic. The infiltrate can extend deeper in the dermis, potentially mimicking a neutrophilic dermatosis such as Sweet syndrome. We present two cases and review the literature to discuss the possibility that a neutrophilic inflammatory infiltrate may be an expected finding in FDE, rather than a histopathologic variant.

Chlorthalidone-Induced Fixed-Drug Eruption: Unmasking an Uncommon Reaction to a Common Diuretic

Fixed-drug eruptions (FDEs) are dermatological reactions characterized by specific skin lesions triggered by certain medications. Our case reports commonly used medications that can cause drug-induced skin reactions. Chlorthalidone, a widely used diuretic, had not been prominently linked to FDEs. Here, we present the case of a 45-year-old African-American male who developed classic FDE skin lesions following the initiation of chlorthalidone therapy. This case underscores the imperative for further investigation and heightened awareness among healthcare professionals regarding chlorthalidone-associated FDEs. Findings suggest that such reactions might be more prevalent than previously acknowledged, underscoring the significance of prompt diagnosis and effective management of drug-induced skin responses. Notably, the patient's lesions showed complete resolution upon discontinuing the diuretic, reinforcing the causal relationship. This case is an essential reminder of the importance of vigilance in monitoring patients for adverse drug reactions, even in unlikely medications, such as chlorthalidone.​​​​​​.

Diagnosis and selection of alternative antibiotics in beta-lactams hypersensitivity reactions: Current recommendations and challenges

Beta-lactam (BLM) antibiotics, including amino-penicillin and cephalosporins, are typically the first-choice treatment for bacterial infections. However, adverse reactions to these antibiotics are frequently reported, causing non-allergist physicians to select alternative broad-spectrum antibiotics that can have harmful consequences. Patients with unclear histories of hypersensitivity reactions to BLMs should undergo an allergy workup to establish a firm diagnosis, particularly when different drugs are prescribed simultaneously. However, finding the safest, most precise, and cost-effective methods for confirming BLMs hypersensitivity and selecting the most appropriate alternative BLM is uncertain, particularly in severe delayed reactions. This review aims to provide data and recommendations on the availability and validity of skin tests (STs), drug provocation test (DPT) protocols, based on the latest published literature and guideline. To make the process more practical, we focused on cross-reactivity between BLMs and diagnostic tests. There are two main novel aspects of this document: 1) For T-cell-mediated reactions, patient stratification into high, moderate, and low-risk groups based on the mortality and morbidity of adverse drug reactions. 2) For IgE-mediated reactions, stratification of individuals with isolated limited urticarial without anaphylaxis in a low-risk group and removal of the extensive limitation.

Case report: Generalized bullous fixed drug eruption mimicking epidermal necrolysis

Generalized bullous fixed drug eruption (GBFDE) is the most severe form of fixed drug eruption and can be misdiagnosed as epidermal necrolysis (EN). We report the case of a 42-year-old male patient presenting with more than 50% skin detachment without defined areas of exanthema or erythema and a history of one prior event of EN caused by acetaminophen (paracetamol), allopurinol, or amoxicillin 1.5 years ago. The initial diagnosis was GBFDE or EN. The histology of a skin biopsy was unable to distinguish between the two diseases. The course of the disease, the later clinical presentation, and the medical and medication history, however, were in favor of a diagnosis of GBFDE with two potentially culprit drugs: metamizole and ibuprofen. Moxifloxacin, enoxaparin sodium, hydromorphone, and insulin human were administered concomitantly, which makes them suspicious as well. Unfortunately, the patient received an additional dose of metamizole, one of the possible causative drugs, and he developed another bullous reaction within 1 month. This led to the diagnosis of GBFDE due to metamizole. This report highlights the challenges of distinguishing two rare diseases and elucidates the importance of distinct clinical presentation and detailed medication history.

Fixed Drug Eruption in a Patient Taking Valacyclovir without Cross-Reactivity to Acyclovir

Fixed drug eruption (FDE) is a well-defined hyperpigmented patch that recurs in a fixed location each time a particular drug is taken. Common causative agents of FDE are non-steroidal anti-inflammatory drugs, non-narcotic analgesics, sedatives, anticonvulsants, sulfonamides, and tetracycline. We report a 33-year-old male who presented with a recurrent, localized, brownish-to-erythematous macule and papules on the peri-philtrum area two hours after taking valacyclovir. Three episodes of valacyclovir ingestion for treatment of Herpes simplex virus infection provoked a similar skin rash at the same site. Histopathology results showed vacuolar degeneration in the basal layer of the epidermis, pigmentary incontinence, and perivascular inflammatory cell infiltration in the papillary dermis. Although patch test and skin prick test showed negative responses to acyclovir and valacyclovir, an intradermal test showed a positive reaction only to valacyclovir. The oral provocation test to acyclovir and valacyclovir showed a positive reaction only to valacyclovir. Through drug history, histopathological examination, patch test, intradermal test, and oral provocation test, we established a final diagnosis of FDE due to valacyclovir without cross-reactivity to acyclovir. To find alternative therapeutic drugs, we suggest diagnostic tests with not only the suspected drugs, but also other drugs in the same class.

Blockade of CD122 on memory T cells in the skin suppresses sclerodermatous graft-versus-host disease

BACKGROUND

Antigen-stimulated naïve T cells differentiate into effector and memory T cells, of which resident memory T (T_RM) cells reside permanently in organ tissues. Involvement of T_RM cells has been indicated in pathological conditions of various skin diseases. CD122, which is the β chain subunit of interleukin (IL)- 2 and IL-15 receptors, is expressed on immune cells including T_RM cells.

OBJECTIVE

To investigate whether CD122 signaling in skin CD8⁺ T_RM cells mediates the development of mucocutaneous graft-versus-host disease (GVHD).

METHODS

We used a genetically modified mouse expressing a membrane-bound form of chicken ovalbumin (OVA) under the control of the keratin 14 promoter, which develops GVHD-like erosive mucocutaneous disease resulting in sclerodermatous disease after transfer of OVA-specific T cell-receptor-transgenic CD8⁺ OT-I cells. Mice with mucocutaneous GVHD were treated with an anti-CD122 blocking antibody.

RESULTS

Administration of an anti-CD122 blocking antibody suppresses the development of acute/chronic GVHD-like mucocutaneous disease in our murine model via the reduction of CD122-expressing memory CD8⁺ T cells, including skin, memory autoaggressive CD8⁺ T cells. Moreover, blockade of CD122, even after the establishment of acute GVHD, inhibited the development of chronic GVHD-like sclerodermatous disease via the reduction of epidermal and dermal T_RM autoaggressive CD8⁺ T cells.

CONCLUSION

Skin memory CD8⁺ T cells in particular mediate the development of mucocutaneous GVHD, and blockade of CD122 may be an effective treatment strategy, especially for sclerodermatous GVHD.

A Fixed-Dose Combination of Ofloxacin-Ornidazole Induced Fixed Drug Eruption: A Case Report

Cutaneous drug eruptions are commonly occurring adverse drug reactions. Food and Drug Association does not recommend a fixed dose combination of ofloxacin-ornidazole; still, it is commonly practised in developing countries. Many patients take this combination of drugs for episodes of gastro-enteritis, often as self-medication. We are reporting a 25 years old male patient presenting with repeated episodes of adverse drug reaction to a fixed dose combination of ofloxacin-ornidazole.

Vesiculobullous Diseases

A diverse range of inflammatory dermatoses are characterized by vesicles or bullae [...]

Kleine Ursache – große Wirkung: Spättyp-Hauttests mit Medikamenten als Auslöser von disseminierten Rezidivexanthemen

Es werden zwei Patienten vorgestellt, die wegen eines streuenden allergischen Kontakt- bzw. Arzneimittelexanthems auf Budesonid bzw. Antibiotika abgeklärt wurden. Bei beiden trat innerhalb einiger Stunden nach Anlegen eines Epikutantests mit Budesonid bzw. Intradermaltesten mit Amoxicillin eine stark positive Hauttestreaktion sowie ein Exanthem auf. Beim ersten Patienten lag eine Sensibilisierung auf die kreuzreagierenden Moleküle Budesonid und Amcinonid, bei der zweiten Patientin eine ausgeprägte Überempfindlichkeit auf Aminopenizilline vor. Aufflammphänomene (Flare-ups) sind v. a. aus der Kontaktallergologie bekannt, können aber auch bei der Abklärung von allergischen Arzneimittelexanthemen auftreten. Systemische Reaktionen vom verzögerten Typ auf Spättyp-Hauttests mit Medikamenten sind relativ selten, können aber eine erhebliche Morbidität bewirken. Verschiedene Formen von Aufflammphänomenen in der Allergologie werden diskutiert.

Fixed Drug Eruption Secondary to Four Anti-diabetic Medications: An Unusual Case of Polysensitivity

We report a case of fixed drug eruption in a 58-year-old lady treated for diabetes with four pharmacologically different anti-diabetic agents that were used at separate times of therapy. Skin manifestations, including erythema, blisters, and ulcers, developed over the right leg each time after the initiation of metformin, gliclazide, vildagliptin, and empagliflozin; and disappeared following the discontinuation of the drugs. Magnesium stearate was the common excipient identified in the four agents. This is an extremely rare case of fixed drug eruption caused by structurally dissimilar drugs.

A Case of Recurrent Fixed Drug Eruption Secondary to Desloratadine

Desloratadine is a second-generation H1-type antihistamine that is widely prescribed for multiple indications including allergic rhinitis and urticaria. It is well-tolerated and is not known to cause cutaneous side effects including fixed drug eruption (FDE). In this report, a case of recurrent fixed drug eruption induced by desloratadine is reported.

A Review of Fixed Drug Eruption with a Special Focus on Generalized Bullous Fixed Drug Eruption

Fixed drug eruption (FDE) is a cutaneous adverse drug reaction characterized by the onset of rash at a fixed location on the body each time a specific medication is ingested. With each recurrence, the eruption can involve additional sites. Lesions can have overlying vesicles and/or bullae, and when they cover a significant percentage of body surface area, the eruption is referred to as generalized bullous fixed drug eruption (GBFDE). Due to the widespread skin denudation that can be seen in this condition, GBFDE may be confused clinically with Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN). While treatments described for GBFDE include supportive care, topical and/or systemic steroids, and, recently, cyclosporine, the mainstay of management involves identifying and discontinuing the causative drug. This review article will provide an overview of FDE with an emphasis on its generalized bullous variant.

Treating Through Drug-Associated Exanthems in Drug Allergy Management: Current Evidence and Clinical Aspects

In the setting of an acute cutaneous adverse drug reaction there is increasing interest in selected phenotypes and hosts to continue drug therapy, especially in settings in which there are limited therapeutic options. This concept of "treating through," defined as the continued use of a drug in the setting of, in particular maculopapular exanthema, potentially avoids unnecessary drug discontinuation. A review of the recent literature, historical viewpoints, and expert opinion are provided within to form recommendations and algorithms for a "treating-through" approach.

Severe Generalized Bullous Fixed Drug Eruption Treated with Cyclosporine: A Case Report and Literature Review

Generalized bullous fixed drug eruptions (GBFDEs) are rare in the paediatric population. We present the case of a 7-year-old girl with GBFDE believed to be secondary to oral ibuprofen, who experienced rapid resolution of lesions and cessation of blistering with a 3-week course of oral cyclosporine. To the best of our knowledge, this is the first report of a paediatric case of GBFDE treated with cyclosporine. In our report, we review published cases of GBFDE in children, and all adult cases managed with cyclosporine.

Pathophysiology of Skin Resident Memory T Cells

Tissue resident memory T (T_RM) cells reside in peripheral, non-lymphoid tissues such as the skin, where they act as alarm-sensor cells or cytotoxic cells. Physiologically, skin T_RM cells persist for a long term and can be reactivated upon reinfection with the same antigen, thus serving as peripheral sentinels in the immune surveillance network. CD8⁺CD69⁺CD103⁺ T_RM cells are the well-characterized subtype that develops in the epidermis. The local mediators such as interleukin (IL)-15 and transforming growth factor (TGF)-β are required for the formation of long-lived T_RM cell population in skin. Skin T_RM cells engage virus-infected cells, proliferate in situ in response to local antigens and do not migrate out of the epidermis. Secondary T_RM cell populations are derived from pre-existing T_RM cells and newly recruited T_RM precursors from the circulation. In addition to microbial pathogens, topical application of chemical allergen to skin causes delayed-type hypersensitivity and amplifies the number of antigen-specific CD8⁺ T_RM cells at challenged site. Skin T_RM cells are also involved in the pathological conditions, including vitiligo, psoriasis, fixed drug eruption and cutaneous T-cell lymphoma (CTCL). The functions of these T_RM cells seem to be different, depending on each pathology. Psoriasis plaques are seen in a recurrent manner especially at the originally affected sites. Upon stimulation of the skin of psoriasis patients, the CD8⁺CD103⁺CD49a^- T_RM cells in the epidermis seem to be reactivated and initiate IL-17A production. Meanwhile, autoreactive CD8⁺CD103⁺CD49a⁺ T_RM cells secreting interferon-γ are present in lesional vitiligo skin. Fixed drug eruption is another disease where skin T_RM cells evoke its characteristic clinical appearance upon administration of a causative drug. Intraepidermal CD8⁺ T_RM cells with an effector-memory phenotype resident in the skin lesions of fixed drug eruption play a major contributing role in the development of localized tissue damage. CTCL develops primarily in the skin by a clonal expansion of a transformed T_RM cells. CD8⁺ CTCL with the pagetoid epidermotropic histology is considered to originate from epidermal CD8⁺ T_RM cells. This review will discuss the current understanding of skin T_RM biology and their contribution to skin homeostasis and diseases.

Probable etoricoxib-induced fixed drug eruption involving the oral mucosa: A case report

Fixed drug eruption (FDE) is a cutaneous adverse drug reaction characterized by recurrence of lesions at the same sites each time a specific drug is taken. Oral mucosal involvement is rare. Nonsteroidal anti-inflammatory drugs are one of the most common offending drug groups in FDE; however, selective cyclooxygenase-2 inhibitors, such as etoricoxib, are rarely implicated. We present a case of oral mucosal and cutaneous FDE induced by etoricoxib that, to the best of our knowledge, is the first reported case of this nature. We describe the diagnostic challenges and review the pertinent literature. The value of drug provocation testing and patch testing in FDE is also discussed.

Lichenoid dermatoses involving the vulva: A clinical-pathologic correlation✰

The lichenoid tissue reaction pattern generally signifies cytotoxic damage to the epithelium. When such reaction pattern occurs on vulvar skin or mucosa, the effects can result in considerable morbidity. None of the entities discussed in this review are entirely unique to the vulva, however, some entities may classically occur at this site, while others tend to be widespread diseases that may incidentally affect vulvar skin and mucosa. Given the complex anatomy of the vulva and the bridging of a site showing both keratinizing squamous epithelium and non-keratinizing squamous mucosa, histopathologic features may display variation in presentation. Although identification of a "lichenoid reaction pattern" alone may provide insight into the disease process, understanding of clinical presentation and specific sites of involvement, along with recognition of the nuanced features of the disease entities can help establish a specific diagnosis. Accurate histopathologic diagnoses by pathologists can improve the ability for treating clinicians to implement timely and effective treatment.

Fixed drug eruptions, bullous drug eruptions, and lichenoid drug eruptions

Drug reactions are among the most common reasons for inpatient dermatology consultation. These reactions are important to identify because discontinuation of the offending agent may lead to disease remission. With the rising use of immunomodulatory and targeted therapeutics in cancer care and the increased incidence in associated reactions to these drugs, the need for accurate identification and treatment of such eruptions has led to the development of the "oncodermatology" subspecialty of dermatology. Immunobullous drug reactions are a dermatologic urgency, with patients often losing a significant proportion of their epithelial barrier; early diagnosis is critical in these cases to prevent complications and worsening disease. Lichenoid drug reactions have myriad causes and can take several months to occur, often leading to difficulties identifying the offending drug. Fixed drug eruptions can often mimic other systemic eruptions, such as immunobullous disease and Stevens-Johnson syndrome, and must be differentiated from them for effective therapy to be initiated. We review the clinical features, pathogenesis, and treatment of immunobullous, fixed, and lichenoid drug reactions with attention to key clinical features and differential diagnosis.

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.

A case of entecavir-associated bullous fixed drug eruption and a review of literature

Fixed drug eruption (FDE) is a type of drug reaction characterized by localized erythema, hyperpigmentation, and bullous at the same site(s), generally observed following every intake of a causative drug. Delayed-type cellular hypersensitivity (Type IVC) is considered to play a role in FDE etiology. Several antibiotics, barbiturates, oral contraceptives, nonsteroidal anti-inflammatory drugs, laxative-containing phenolphthalein, metronidazole, and quinine are known to be the primary drugs responsible for FDE. Bullous FDE, on the other hand, is a relatively rare form of FDE. Hepatitis B is a significant worldwide health problem, and entecavir is a common nucleoside (deoxyguanosine) analog used for treating hepatitis B; however, it has various side effects, such as lactic acidosis, myalgia, azotemia, hypophosphatemia, headache, diarrhea, pancreatitis, and neuropathy, and, in rare cases, cutaneous drug eruption. Our aim is to present a case of entecavir-associated bullous drug reaction, which has not been reported in the literature. Furthermore, we performed a review of literature to compile previously reported entecavir-associated drug reactions.

Skin-resident memory T cells as a potential new therapeutic target in vitiligo and melanoma

Tissue-resident memory T (T_RM ) cells are abundant in the memory T cell pool and remain resident in peripheral tissues, such as the skin, where they act as alarm sensors or cytotoxic killers. T_RM cells persist long after the pathogen is eliminated and can respond rapidly upon reinfection with the same antigen. When aberrantly activated, skin-located T_RM cells have a profound role in various skin disorders, including vitiligo and melanoma. Autoreactive T_RM cells are present in human lesional vitiligo skin and mouse models of vitiligo, which suggests that targeting these cells could be effective as a durable treatment strategy for vitiligo. Furthermore, emerging evidence indicates that induction of melanoma-reactive T_RM cells is needed to achieve effective protection against tumor growth. This review highlights seminal reports about skin-resident T cells, focusing mainly on their role in the context of vitiligo and melanoma, as well as their potential as therapeutic targets in both diseases.

Ciprofloxacin-Induced Bullae of the Lower Extremity: A Case of a Fixed Drug Reaction

Cutaneous adverse drug reactions make up 1% to 2% of all adverse drug reactions. From these adverse cutaneous drug reactions, 16% to 21% can be categorized as fixed drug reactions (FDR). Fixed drug reactions may show diverse morphology including but not limited to the following: dermatitis, Stevens-Johnson syndrome, urticaria, morbilliform exanthema, hypersensitivity syndrome, pigmentary changes, acute generalized exanthematous pustulosis, photosensitivity, and vasculitis. An FDR will occur at the same site because of repeated exposure to the offending agent, causing a corresponding immune reaction. There are many drugs that can cause an FDR, such as analgesics, antibiotics, muscle relaxants, and anticonvulsants. The antibiotic ciprofloxacin has been shown to be a cause of cutaneous adverse drug reactions; however, the fixed drug reaction bullous variant is rare. This case study was published to demonstrate a rare adverse side effect to a commonly used antibiotic in podiatric medicine.

Common Annular Lesions in the Pediatric Population: Part 2

Rash is a common chief complaint for patients presenting to their physician, especially within the pediatric field. The ability to distinguish characteristics of a rash, including morphology, distribution, and configuration, is critical to forming the differential diagnosis. This is the second article of a 2-part review that discusses the common rashes that present in an annular configuration. This articles discuss the presentation, diagnosis, and treatment of fixed drug eruptions, lupus erythematosus, erythema multiforme, urticaria, and erythema migrans. Although this review is not inclusive of all conditions that present with annular lesions, it can serve as a starting point for physicians managing a patient with these complaints. [Pediatr Ann. 2019;48(3):e135-e138.].

Inverse similarity and reliable negative samples for drug side-effect prediction

BACKGROUND

In silico prediction of potential drug side-effects is of crucial importance for drug development, since wet experimental identification of drug side-effects is expensive and time-consuming. Existing computational methods mainly focus on leveraging validated drug side-effect relations for the prediction. The performance is severely impeded by the lack of reliable negative training data. Thus, a method to select reliable negative samples becomes vital in the performance improvement.

METHODS

Most of the existing computational prediction methods are essentially based on the assumption that similar drugs are inclined to share the same side-effects, which has given rise to remarkable performance. It is also rational to assume an inverse proposition that dissimilar drugs are less likely to share the same side-effects. Based on this inverse similarity hypothesis, we proposed a novel method to select highly-reliable negative samples for side-effect prediction. The first step of our method is to build a drug similarity integration framework to measure the similarity between drugs from different perspectives. This step integrates drug chemical structures, drug target proteins, drug substituents, and drug therapeutic information as features into a unified framework. Then, a similarity score between each candidate negative drug and validated positive drugs is calculated using the similarity integration framework. Those candidate negative drugs with lower similarity scores are preferentially selected as negative samples. Finally, both the validated positive drugs and the selected highly-reliable negative samples are used for predictions.

RESULTS

The performance of the proposed method was evaluated on simulative side-effect prediction of 917 DrugBank drugs, comparing with four machine-learning algorithms. Extensive experiments show that the drug similarity integration framework has superior capability in capturing drug features, achieving much better performance than those based on a single type of drug property. Besides, the four machine-learning algorithms achieved significant improvement in macro-averaging F1-score (e.g., SVM from 0.655 to 0.898), macro-averaging precision (e.g., RBF from 0.592 to 0.828) and macro-averaging recall (e.g., KNN from 0.651 to 0.772) complimentarily attributed to the highly-reliable negative samples selected by the proposed method.

CONCLUSIONS

The results suggest that the inverse similarity hypothesis and the integration of different drug properties are valuable for side-effect prediction. The selection of highly-reliable negative samples can also make significant contributions to the performance improvement.

Pediatric drug hypersensitivity: which diagnostic tests?

Along with the anamnesis and clinical evaluation, diagnostic tests are one of the mainstream key points in the evaluation and management of drug hypersensitivity reactions (DHR). A wide knowledge gap, both in diagnosis and management of pediatric DHR, must be filled.  Only a few published studies evaluated sensitivity and specificity of skin and in vitro tests in children. However, selected case series show that diagnostic work-up for adults could be useful, with some limitations, in pediatric age. Indeed, despite improvement in in vivo and in vitro diagnosis, drug provocation test remains the gold standard in pediatric age, too. Unmet needs in children include multi-centric studies on incidence of DHR, utility and feasibility of in vivo and in vitro diagnostic tests and specifically dedicated guidelines for the diagnosis and management of DHR in children.

A Probable Case of Mucosal Fixed Drug Eruption Following Treatment with Silodosin

A fixed drug eruption consists of erythematous patches that appear on the skin and/or mucous membranes following administration of a drug which, once healed, leaves residual hyperpigmentation. We report a 76-year-old male who presented to the Thriasio General Hospital, Athens, Greece, in 2016 with erythema, oedema and blistering of the lower lip and glans penis following the administration of silodosin for benign prostatic hyperplasia. The eruption regressed two weeks after silodosin was discontinued.

Resident-Memory T Cells in Tissue-Restricted Immune Responses: For Better or Worse?

Tissue-resident-memory CD8+ T cells (T_RM) have been described as a non-circulating memory T cell subset that persists at sites of previous infection. While T_RM in all non-lymphoid organs probably share a core signature differentiation pathway, certain aspects of their maintenance and effector functions may vary. It is well-established that T_RM provide long-lived protective immunity through immediate effector function and accelerated recruitment of circulating immune cells. Besides immune defense against pathogens, other immunological roles of T_RM are less well-studied. Likewise, evidence of a putative detrimental role of T_RM for inflammatory diseases is only beginning to emerge. In this review, we discuss the protective and harmful role of T_RM in organ-specific immunity and immunopathology as well as prospective implications for immunomodulatory therapy.

Pathogenic role of tissue-resident memory T cells in autoimmune diseases

The tissue-resident memory T (T_RM) cells constitute a newly identified subset of memory T cells which are non-circulating and they persist for long-term in epithelial barrier tissues, including skin, lung, gastrointestinal tract and reproductive tract, and in non-barrier tissues, including brain, kidney, pancreas and joint. These cells provide rapid on-site immune protection against previous exposed pathogens in peripheral tissues. There cells are transcriptionally, functionally and phenotypically distinguished from circulating effector memory T cells. In addition to their protective functions, increasing evidence reveals that autoreactive and/or aberrantly activated T_RM cells may be involved in the pathogenesis of autoimmune disorders such as psoriasis and, as recently reported, may contribute to vitiligo, autoimmune hepatitis and rheumatoid arthritis. Therefore, this review aims to summarize the current progress in the biology of T_RM cells, such as the newly identified T_RM markers, upstream regulators, and the functions of T_RM cells. We also discuss the contributions of T_RM cells to the development of autoimmunity to broaden our understanding of autoimmune diseases and to provide novel potential therapeutic strategies for these diseases.