Progress in the understanding of the pathology and pathogenesis of cutaneous drug eruptions : implications for management

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.

Disorders of Facial Hyperpigmentation

Disorders of hyperpigmentation are common and challenging conditions which can arise due to a myriad of etiologic factors. Many of them can present across skin types but are more common in skin of color individuals with Fitzpatrick skin types III-VI. Facial hyperpigmentation, in particular, can have a significant impact on the quality of life of affected individuals due to its increased visibility. This article provides a comprehensive review of disorders of facial hyperpigmentation including epidemiology, pathogenesis, diagnostic considerations, and treatment approaches for these conditions.

Autoimmune pre-disease

Approximately 5% of the world-wide population is affected by autoimmune diseases. Overall, autoimmune diseases are still difficult to treat, impose a high burden on patients, and have a significant economic impact. Like other complex diseases, e.g., cancer, autoimmune diseases develop over several years. Decisive steps in the development of autoimmune diseases are (i) the development of autoantigen-specific lymphocytes and (often) autoantibodies and (ii) potentially clinical disease manifestation at a later stage. However, not all healthy individuals with autoantibodies develop disease manifestations. Identifying autoantibody-positive healthy individuals and monitoring and inhibiting their switch to inflammatory autoimmune disease conditions are currently in their infancy. The switch from harmless to inflammatory autoantigen-specific T and B-cell and autoantibody responses seems to be the hallmark for the decisive factor in inflammatory autoimmune disease conditions. Accordingly, biomarkers allowing us to predict this progression would have a significant impact. Several factors, such as genetics and the environment, especially diet, smoking, exposure to pollutants, infections, stress, and shift work, might influence the progression from harmless to inflammatory autoimmune conditions. To inspire research directed at defining and ultimately targeting autoimmune predisease, here, we review published evidence underlying the progression from health to autoimmune predisease and ultimately to clinically manifest inflammatory autoimmune disease, addressing the following 3 questions: (i) what is the current status, (ii) what is missing, (iii) and what are the future perspectives for defining and modulating autoimmune predisease.

Amoxicillin/Clavulanic Acid-Induced Symmetric Drug-Related Intertrigious and Flexural Exanthema

β-Lactams, particularly penicillins, may cause several allergic reactions. We described symmetric drug-related intertriginous and flexural exanthema (SDRIFE) illness in this case, a rare instance of systemic contact dermatitis caused by amoxicillin/clavulanic acid that needs to be considered in the differential diagnosis. A 65-year-old male patient was admitted to our Allergy Outpatient Clinic because of increased blue-purple pigmentation on the flexural surfaces of the hip, forearm, axilla, and posterior face of the neck. The patient was receiving a combination of angiotensin receptor blocker (ARB) and hydrochlorothiazide diuretic medication for hypertension. The patient used an antibiotic containing amoxicillin three months ago; As a result, there was localized redness, itching, and black spotting without any systemic symptoms. Similarly, the patient reported that when he used amoxicillin for an upper respiratory tract infection eight months ago, he experienced similar side effects within 20 days and recovered when he applied corticosteroid ointment. Due to the symmetrical site involvement following the consumption of penicillin group antibiotics with a five-month gap and subsequent comparable reactions in our patient, SDRIFE was taken into consideration. The results of the skin punch biopsy identified Baboon Syndrome (SDRIFE). Treatment with topical corticosteroids and antihistamines began. Clinically speaking, SDRIFE is distinguished by significant erythema of the gluteal/perianal area and/or V-shaped erythema of the inguinal/perigenital area, symmetric involvement of at least one other intertriginous or flexural area, and the absence of systemic signs or symptoms. The possibility that the medication may have contributed to the patient's erythematous eruption in the flexural regions should be taken into account, and the patient should be advised to stop taking the medication and not use it again.

Revisiting the question of toxidermia classification

In connection with the upcoming transition to the International Classification of Diseases and Health-related Problems of the eleventh revision (ICD-11), the authors of the article propose to replace the term toxidermy with a new, widely used in the world term drug-induced skin reactions. For standardization of definitions and diagnostic criteria, a unified working classification of this group of diseases is based on a mixed principle clinical manifestations (primary morphological elements of skin rash), etiological and pathogenetic aspects are taken into account. The applied unified classification of drug-induced skin reactions is proposed for discussion.

Histopathologic Features of Maculopapular Drug Eruption

Background: Cutaneous adverse drug reaction (CADR) is common in both inpatient and outpatient clinical settings and has been associated with a large variety of medications. Drug reactions represent a significant burden to the healthcare system due to increased hospital stay durations and associated costs. Moreover, some of these reactions may be life-threatening. The most common clinical manifestation of a CADR is a maculopapular drug eruption (MDE). Due to its many clinical mimics and associations with a variety of histopathologic patterns, maculopapular drug eruption is difficult to definitively diagnose from both a clinical and histopathological perspective. Summary: We reviewed the clinical and histopathologic features of 327 cases of MDE from several studies in the literature and summarized characteristic histopathologic findings and their frequencies of occurrence. We found that the most common and suggestive histopathologic features of MDE were epidermal spongiosis, lymphocytic infiltrate, and occasional necrotic keratinocytes; interface change at the DEJ; superficial perivascular and interstitial lymphocytic infiltrate with or without eosinophils and neutrophils in the mid-to-deep dermis and mild papillary dermal edema; and dilation of superficial vessels. The presence of multiple histopathologic patterns within the same tissue specimen is also suggestive of MDE. This review and analysis suggest that a biopsy may improve the diagnostic accuracy by both establishing common and uncommon features associated with MDE and reviewing features that help to exclude other causes of maculopapular eruption. Key Message: Histopathologic criteria for the diagnosis of MDE, while not entirely specific, may aid in establishing a differential that includes a drug eruption. Thus, a biopsy can be a helpful diagnostic tool when MDE is suspected by demonstrating findings suggestive of MDE or by ruling out clinical mimics. However, biopsy results cannot be used in isolation as clinical-pathologic correlation is paramount in MDE.

Impact of Climatic Variations on Drug-induced Skin Reactions in Two Different Regions of India

BACKGROUND

Around 2-3% of hospitalizations have been reported due to dermatological adverse drug reactions. Recent studies suggest that climatic variations affect the skin barrier function and extreme conditions aggravate skin disorders.

OBJECTIVE

The present study was designed to compare the impact of climatic variations on drug-induced skin reactions in the Northern and Eastern regions of India.

METHODS

We performed a one-year retrospective study to evaluate the impact of climatic variations (temperature and humidity) on drug-induced skin reactions in the Eastern (Kalyani, West Bengal) and Northern (Karnal, Haryana) regions. Drug-induced skin reactions were reported month-- wise in both the Eastern and Northern regions. Temperature and humidity levels were also noted month-wise in both regions. The direct correlation between climatic variations and the number of drug reactions were assessed using Pearson's correlation and quadratic regression analysis.

RESULTS AND DISCUSSION

Overall, 99 and 81 dermatological adverse drug reactions were reported in tertiary care hospitals in the Northern and Eastern regions, respectively. During the summer season, the humidity level was found to be low in the Northern region as compared to the Eastern region. During this period, drug-induced skin reactions were reported significantly (p<0.05) more in the Northern region as compared to the Eastern region. Furthermore, quadratic regression analysis revealed that climatic variations contributed to drug reaction variability in the Northern region (68.5%) and Eastern region (23.5%).

CONCLUSION

Therefore, the difference in the prevalence of drug-induced skin reactions may be related to the different climatic conditions among these two regions. Further studies in controlled climatic conditions should be performed for definitive correlations and to look into possible solutions.

Diagnoses of hospitalized patients with skin abnormalities prompting biopsy by consulting dermatologists: A 3-year review from a tertiary care center

Background

Dermatologists play an important role in diagnosing and managing hospitalized patients with cutaneous abnormalities. Skin biopsies remain an indispensable tool for aiding dermatologists in accurate diagnosis and treatment. We aimed to determine the range of conditions, and the most common conditions, prompting skin biopsy by dermatology hospital consultation (HCON) services to aid in evaluation of hospitalized patients.

Methods

All hospitalized patients seen by a single tertiary care center dermatology HCON service between 2015 and 2018 who had associated skin biopsies were identified. Histologic features and clinical diagnoses of each patient were classified into 13 histologic reaction pattern categories.

Results

Eight hundred and thirty one inpatients evaluated by our dermatology HCON service had 914 skin biopsies. The most frequent diagnostic categories prompting biopsy were vasculopathic (17.6%), interface dermatitis (16.5%), infectious (12.6%), and spongiotic dermatitis (10.9%). The most frequent diagnostic categories included drug reaction (13.2%), leukocytoclastic vasculitis (8.5%), skin cancer (5.4%), graft‐vs‐host disease (3.5%), connective tissue disease (3.3%), and calciphylaxis (3.0%).

Conclusion

Our study suggests a variety of serious diseases affecting inpatients prompts biopsy by dermatology consultation services. Educational curricula for dermatology and pathology residents, fellows, and staff designed with these data may enhance knowledge that improves the quality of inpatient dermatology care.

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.

Development of Drug-Induced Inverse Psoriasis in a Patient with Crohn's Disease

Crohn’s disease is difficult to manage and often requires multiple medications. While these drugs vastly improve quality of life, physicians must monitor for adverse events. We report a case of a flare of inverse psoriasis after 15 months of treatment with ustekinumab. This is the third reported case of a flare of drug-induced psoriasis with ustekinumab, and it is the first reported case with an inverse presentation; however, the clinical picture is confounded by concomitant use of hydroxychloroquine. Inverse psoriasis is a rare variant of drug-induced psoriasis of which physicians must be cognizant while treating patients with Crohn’s disease.

Adverse drug reactions and organ damage: The skin

Cutaneous adverse drug reactions are frequent, affecting 2-3% of hospitalized patients and in one twentieth of them are potentially life-threatening. Almost any pharmacologic agent can induce skin reactions, and certain drug classes, such as non-steroidal anti-inflammatory drugs, antibiotics and antiepileptics, have drug eruption rates ranging from 1% to 5%. Cutaneous drug reactions recognize several different pathomechanisms: some skin manifestations are immune-mediated like allergic reactions while others are the result of non immunological causes such as cumulative toxicity, photosensitivity, interaction with other drugs or different metabolic pathways. Cutaneous adverse drug reactions can be classified into two groups: common non-severe and rare life-threatening adverse drug reactions. Non-severe reactions are often exanthematous or urticarial whereas life-threatening reactions typically present with skin detachment or necrosis of large areas of the body and mucous membrane involvement, as in the Stevens-Johnson syndrome or toxic epidermal necrolysis. Clinicians should carefully evaluate the signs and symptoms of all cutaneous adverse drug reactions thought to be due to drugs and immediately discontinue drugs that are not essential. Short cycles of systemic corticosteroids in combination with antihistamines may be necessary for widespread exanthematous rashes, while more aggressive corticosteroid regimens or intravenous immunoglobulins associated with supportive treatment should be used for patients with Stevens-Johnson syndrome or toxic epidermal necrolysis.

Metronidazole-Induced Bullous Pemphigoid: A Case Report

Bullous pemphigoid is an autoimmune cutaneous blistering disorder, the exact pathogenesis of which is still not fully elucidated. Drug-induced bullous pemphigoid eruptions are rare but have been reported earlier with the use of frusemide, psoralens, ibuprofen, galantamine hydrobromide, ACE inhibitors like captopril, spironolactone, penicillin, ampicillin, levofloxacin, penicillamine. We hereby report a case of metronidazole induced bullous pemphigoid (BP) in a 52-year-old male patient suffering from liver abscess following 4 days of drug administration. The skin biopsy findings obtained from the patient were consistent with the diagnosis of bullous pemphigoid (BP). Metronidazole was discontinued and symptomatic treatment was offered to the patient. Following withdrawal of metronidazole, the bullae subsided in the next 7-10 days without any significant residual scarring. The causality assessment performed as per the Naranjo algorithm revealed the case to be probable (Naranjo score 7).

Drug-induced skin reactions: a pathologist viewpoint

Cutaneous drug reactions are common adverse effects that occur in about 2-3% of the hospitalized patients. They have both immunologic and non-immunologic underlying mechanisms. These reactions are clinically and histologically similar to dermatoses. Their significant clinical indicators include: history of drug intake, atypical clinical features and improvement after cessation of the offending drugs. Their diagnostic histological clues include the presence of mixed histological patterns, apoptotic keratinocytes, eosinophils (dermis and epidermis), papillary dermal edema and extravasations of erythrocytes. However, no single clinical or histological feature is specific of drug eruptions. This work attempts to classify the histomorphologic reactions to various drugs in defined categories for assistance in morphologic diagnosis.

Unfamiliar Manifestations of Anti-tubercular Therapy

Cutaneous drug reactions are frequent in hospitalized patients and vary from simple manifestations like rash and erythema to severe life threatening conditions like angio-oedema, erythroderma, Stevens-Johnson syndrome and toxic epidermal necrolysis. However drug eruptions with antitubercular drugs are largely unknown except few case reports. We highlight here one similar case which presented with pleomorphic cutaneous manifestations after taking anti tubercular therapy and closely mimicked vasculitis. But when the offending drugs were stopped the lesions disappeared and the patient improved.

A case report of hydralazine-induced skin reaction: Probable toxic epidermal necrolysis (TEN)

PATIENT

Female, 75 FINAL DIAGNOSIS: Hypertensive crisis with multi organ failure Symptoms: Anemia • general weakness • hypokalemia • nausea • tachycardia

MEDICATION

- Clinical Procedure: - Specialty: Cardiology.

OBJECTIVE

Unexpected drug reaction.

BACKGROUND

Skin reactions are common adverse drug reactions and may include angioedema, erythroderma, Stevens-Johnson syndrome, and toxic epidermal necrolysis (TEN). TEN is a rare but serious reaction characterized by widespread erythema, necrosis, and bullous detachment of the epidermis and mucous membranes.

CASE REPORT

An elderly woman presented with generalized weakness and nausea, associated with a hypertensive crisis. Following the initiation of hydralazine, well-demarcated erythematous maculopapular rashes appeared on her right forearm and left leg, which transformed into a bullous rash. Subsequently, a similar patch appeared on her left forearm, with a similar progression and associated with generalized edema of the extremities. A clinical diagnosis of drug-induced toxic epidermal necrolysis was made and hydralazine was discontinued. Following this, the skin lesions improved, with complete subsequent resolution. Skin biopsy was not performed due to the rapid resolution of the lesions. A negative screen for autoantibodies ruled out systemic lupus erythematosus, scleroderma, and other undifferentiated connective tissue disorders. After re-administration of hydralazine, the same lesions appeared again, which again resolved after its discontinuation, thus confirming our initial clinical suspicion. Treatment is immediate discontinuation of the offending drug and supportive care.

CONCLUSIONS

Clinical awareness with close monitoring is important for the identification of a rare adverse drug reaction, which can be fatal if not diagnosed and treated promptly.

Severe photosensitivity reaction induced by topical diclofenac

Albeit uncommon, photosensitivity reaction induced by diclofenac can be an unfortunate adverse reaction complicating its use as a topical analgesic. We here present a case of a patient who suffered such a reaction as a result of exposure to diclofenac, employed as a topical analgesic for low backache. The lesions healed with conservative management without extensive scarring or other complications.

A review of cutaneous drug eruptions

Cutaneous drug eruptions can range from an asymptomatic rash to a life-threatening emergency. Because of the high frequency, morbidity, and potential mortality associated with drug eruptions, patients with possible drug reactions should promptly be recognized, worked up, and treated. Drug reactions are common in the elderly population due to age-related alterations in metabolism, excretion of medications, and polypharmacy. This review discusses the epidemiology, pathogenesis, clinical presentation, diagnosis, and management of drug eruptions that providers commonly encounter in the care of the geriatric population. An algorithm for an approach to patients with a suspected drug eruption is presented.

Involvement of the immune system in idiosyncratic drug reactions

There is strong evidence that most idiosyncratic drug reactions (IDRs) are immune-mediated and are caused by reactive metabolites of a drug rather than by the drug itself. Several hypotheses have been proposed by which a drug could induce an immune response. The major hypotheses are the hapten hypothesis and the danger hypothesis; however, the characteristics and spectrum of IDRs are different with different drugs, and this likely reflects mechanistic differences; therefore, no one hypothesis is likely to explain all IDRs. Some IDRs appear to involve epigenetic effects, direct activation of antigen-presenting cells, or disturbing the normal balance of the immune system. It has been suggested that many cases of idiosyncratic liver injury are not immune-mediated, and other mechanisms such as mitochondrial injury may be involved. It is essential that any hypothesis be consistent with the clinical characteristics of the IDR. Although the characteristics of most idiosyncratic liver injury do not suggest that mitochondria are the major target, it is quite possible that milder mitochondrial injury could stimulate an immune-mediated reaction. The observation that IDRs can vary widely among different drugs and different patients is most easily explained by an immune mechanism in which the target of the immune response is different.

Drug-induced autoimmunity

PURPOSE OF REVIEW

This review aims to draw attention to the increased spectrum of the features of drug-induced autoimmunity (DIA), including both clinical and autoantibody profiles in addition to the potential chronicity of the syndrome.

RECENT FINDINGS

In recent years, not only has the number of medications causing DIA increased but the spectrum of the features has broadened as well. With the use of newer medications, especially biologics, mostly directed towards immune system manipulation, the range of signs and symptoms of DIA as well as the patterns of autoantibody profiles have widened. Rashes and visceral involvement have started to be reported more often, especially with tumor necrosis factor antagonists. In addition, autoantibodies such as antidouble-stranded DNA, which are usually seen with idiopathic systemic lupus erythematosus, are appearing in place of the antihistone antibodies, typically found in drug-induced lupus. Finally, some medications have been implicated in causing the very same entity, which they may be used to treat. It is clear that progress in the field of pharmacogenetics and pharmacogenomics will help further our understanding of these and other adverse effects of medications.

SUMMARY

Even though DIA has been known for many years, the underlying mechanisms remain unclear. However, with recently described new and unexpected features, novel hypotheses have been proposed, thus opening doors to further research in understanding these mechanisms.

Cutaneous drug eruptions: a 5-year experience

BACKGROUND

The diversity of cutaneous drug eruptions encompasses many clinicopathologic entities.

METHODS

Cases with a pathologic diagnosis of drug eruption from 2000 to 2005 were retrieved from our institution. The histologic slides were reviewed, the patterns of inflammatory changes were recorded, and a chart review was performed.

RESULTS

The majority of the cases (94%) were "morbilliform"-type rashes. Eighty-two percent of cases exhibited an inflammatory infiltrate confined to the superficial dermis. Eighty percent exhibited a perivascular and interstitial pattern of dermal infiltrate. The infiltrate was composed of lymphocytes and eosinophils in approximately 29% of cases, lymphocytes and neutrophils in approximately 10% of cases, and lymphocytes, eosinophils, and neutrophils in approximately 21% of cases. Eosinophils were present in only 50% of cases. Approximately half (53%) of the cases exhibited epidermal-dermal interface changes.

LIMITATIONS

The cases were limited to those with a pathologic diagnosis of cutaneous drug reaction, thereby excluding any cases with drug-induced disease not specifically diagnosed (histologically) as such.

CONCLUSIONS

While the histologic features of most drug eruptions are not entirely specific, the finding of superficial infiltrates composed variably of lymphocytes, neutrophils, and eosinophils, either with or without interface changes, should suggest the possibility of a morbilliform drug eruption. Clinical correlation is very helpful to confirm the diagnosis. To our knowledge, this study is the most extensive documenting the histologic findings in morbilliform drug eruptions.

Diffuse exanthema in a patient receiving varenicline

PURPOSE

A diffuse exanthema in a patient receiving varenicline is reported.

SUMMARY

A 71-year-old white woman, who was initially admitted to the hospital for elective vascular bypass surgery, had a three-day history of a diffuse rash, severe itching, and moderate headache. Her symptoms started two days before her admission. She denied having a fever, chills, nausea, vomiting, diarrhea, and flulike symptoms. She also denied having had contact with anyone who was ill, tick or insect bites, exposure to cats, or any changes in her diet, habits, or personal hygiene. Her medical problems included peripheral vascular disease, chronic obstructive pulmonary disease (COPD), dyslipidemia, hypertension, and hypothyroidism. In addition to several medications she had been taking for over 2 years, she had been taking varenicline as an aid for smoking cessation for eight days. The patient had been smoking for 40 years. The bright-red rash covered 70% of her torso and four extremities. She had mild swelling in her cheeks, but not on the eyelids or lips. Both of her lungs were clear on auscultation, with distant breath sounds caused by her COPD. Varenicline was discontinued, and her symptoms had completely resolved by the eighth day following discontinuation of the medication. While it is possible that other medications caused her symptoms, she had been taking most of them for over 2 years and all of them for over 1 year. Also, continuation of these drugs did not prevent her symptoms from resolving, nor did it cause a recurrence of the skin reaction.

CONCLUSION

A patient developed diffuse exanthema after being treated with varenicline.

Interface dermatitis

Interface dermatitis can be classified based upon the cell type that dominates the infiltrate (ie, neutrophilic, lymphocytic, or lymphohistiocytic) or by the intensity of the interface inflammation. Regarding lymphocytic interface dermatitis, there are 2 broad categories: cell-poor interface dermatitis, when only a sparse infiltrate of inflammatory cells is present along the dermoepidermal junction, or cell rich, which typically occurs as a heavy bandlike infiltrate that obscures the basal layers of the epidermis. In the case of lymphocytic interface dermatitis, the latter is often termed a lichenoid interface dermatitis. This review focuses upon the mononuclear cell-predominant forms of interface dermatitis.

Phenytoin desensitization monitored by antigen specific T cell response using carboxyfluorescein succinimidyl ester dilution assay

We evaluated drug-specific T cell responses in a patient with refractory partial seizures and paroxysmal kinesigenic choreoathetosis successfully treated with clinical desensitization to phenytoin. Drug-induced lymphocyte transformation test before desensitization was negative with a stimulation index of 130%. The frequencies and cytokine-producing phenotypes of phenytoin-specific T cells were examined simultaneously by using a carboxyfluorescein succinimidyl ester (CFSE) dilution assay. Before desensitization, the proportion of CFSElow CD4+ cells in whole CD4+ was 3.09%; 13.6% of CFSElow CD4+ cells were stained with anti-interferon gamma antibody. After desensitization, phenytoin-specific CFSElow CD4+ cells decreased to background level. These results indicate that CFSE dilution assay will be useful for the diagnosis and monitoring of drug hypersensitivity.

Adverse cutaneous drug eruptions and HIV: a clinician's global perspective

Adverse drug reactions (ADRs) are common and mostly avoidable. Some ADRs cannot as yet be predicted, but at-risk populations/patients and high-risk drugs are identifiable. HIV-infected patients are at risk of developing cutaneous ADRs, especially Stevens-Johnson syndrome, toxic epidermal necrolysis, and drug hypersensitivity syndrome. Multiple factors of causation variably present in patients with HIV infection best explain the pathogenesis of these cutaneous ADRs. When no effective alternate therapy is available, drug rechallenge in HIV-infected patients can be attempted with little morbidity or mortality if done according to rationalized protocols.

Immune response to xenobiotics in the skin: from contact sensitivity to drug allergy

Skin is the most frequent target of adverse drug reactions. These cutaneous drug reactions (CDRs) show varied clinical manifestations ranging from mildly discomforting rashes to life-threatening Stevens-Johnson syndrome or toxic epidermal necrolysis. Most CDRs appear to be immune mediated, although the mechanism by which they are initiated remains unclear. In this review, current knowledge of the mechanisms by which xenobiotics provoke immune responses in the skin after epicutaneous administration and how similar reactions may occur after systemic routes are summarised. This review also discusses a variety of genetic or environmental factors that may determine the susceptibility of individuals towards immune responses in skin following drug exposure.

Adverse antibiotic-induced eruptions associated with epstein barr virus infection and showing Kikuchi-Fujimoto disease-like histology

The antibiotic-induced eruption of infectious mononucleosis is a well-known clinical phenomenon. Latent viral infection with herpesviridae (eg, human herpes virus 6 (HHV-6) and Epstein-Barr virus (EBV)) is suspected to play a role in the drug hypersensitivity syndrome. The cutaneous pathologic findings have not been reported in the former, and are infrequently reported in the latter entity. Herein, we describe the biopsy findings of a cefprozil-induced rash in infectious mononucleosis and a minocycline-associated drug hypersensitivity syndrome. Biopsy of these exanthematous eruptions revealed an acute vacuolar interface superficial and deep perivascular and interstitial lymphocytic dermatitis. CD8(+) lymphocytes predominated and were associated with non-neutrophilic nuclear (karyorrhectic) debris and numerous small CD68(+) and CD123(+) monocytes. These aforementioned features have been described in cutaneous lesions of Kikuchi-Fujimoto disease, an entity whose clinicopathologic findings overlap with both infectious mononucleosis and lupus erythematosus. Serologic evidence of active and chronic active EBV infection was found in both patients, respectively. No evidence of EBV or HHV6 was found in the cutaneous lesions. Plasmacytoid monocytes (CD68(+)/CD123(+) cells), which produce type I interferon, are believed to play a role in viral immunity by protecting other cells from viral infections and promoting survival of antigen-activated T cells. Their presence in these two putative examples of viral-drug immune dysregulation could be a clue to pathogenesis and represent a common cellular component of some adverse cutaneous drug eruptions.

Histopathology of drug-induced exanthems: is there a role in diagnosis of drug allergy?

PURPOSE OF REVIEW

Cutaneous eruptions are among the most common adverse drug reactions and may often represent a challenging diagnostic problem. This review focuses on histopathological and immunohistochemical findings of drug-induced maculo-papular exanthems and discusses the value of skin biopsies and consequent histopathological examination in the diagnosis of these reactions.

RECENT FINDINGS

Data from immunohistological studies indicate that CD4+ T cells expressing cytotoxic granule proteins such as perforin and granzyme B are critically involved in the pathogenesis and contribute to the generation of typical histopathological features of drug-induced maculo-papular exanthems, i.e. an interface dermatitis with vacuolar alteration and some apoptotic basal keratinocytes. In addition, an upregulation of both type 1 (i.e. IFN-gamma, TNF-alpha) and type 2 (i.e. IL-5) cytokines has been reported. IL-5 together with other chemokines (i.e. eotaxin/CCL-11) provides an explanation for tissue eosinophilia, which may be suggestive of a drug eruption if present.

SUMMARY

There are no absolute histological or immunohistological criteria for the diagnosis of drug-induced maculo-papular exanthems and even if the observed histological changes are compatible with a drug-induced eruption, biopsy may not definitely exclude alternative causes since there is considerable overlap with features seen in other entities. In mild cases with no severe signs or symptoms and a clear temporal relationship, clinical information and the morphologic pattern of skin lesions are often sufficient for diagnosis. However, in complex and severe cases or when the precise morphology is unclear, histopathological findings may provide some clues and assist in reaching a correct diagnosis.

Drug-induced exanthems

Cutaneous adverse reactions to drugs can comprise a broad spectrum of clinical and histopathological features. Recent evidence from immunohistological and functional studies of drug-reactive T cells suggest that distinct T-cell functions may be responsible for this broad spectrum of different clinical reactions. Maculopapular exanthems represent the most commonly encountered cutaneous drug eruption. Previous studies on maculopapular exanthems indicate that drug-specific CD4+ T cells expressing cytotoxic granule proteins such as perforin and granzyme B are critically involved in killing activated keratinocytes. These cells are particularly found at the dermo-epidermal junction and may contribute to the generation of vacuolar alteration and destruction of basal keratinocytes, which are typical found in drug-induced maculopapular exanthems. In contrast to maculopapular exanthems, the preferential activation of drug-specific cytotoxic CD8+ T cells may lead to more severe reactions like bullous drug eruptions. Furthermore, activation of drug-specific T with distinct cytokine and chemokines profiles may also explain the different clinical features of drug-induced exanthems. IL-5 and eotaxin are upregulated in maculopapular exanthems and explain the eosinophilia often found in these reactions.

Olanzapine-induced vasculitis

INTRODUCTION

Elderly patients are particularly vulnerable to adverse drug reactions as a result of polypharmacy and metabolic changes associated with aging. We present a case of leukocytoclastic vasculitis induced by olanzapine, a medication commonly used in elderly patients.

CASE SUMMARY

An 82-year-old woman was admitted to the extended-care center for short-term rehabilitation after prolonged hospitalization for a pulmonary embolism requiring mechanical ventilation. The pulmonary problem resolved, but her hospitalization and subsequent rehabilitation were complicated by agitated delirium, which was treated with olanzapine and modification of contributory factors. At the time of admission to the rehabilitation facility, the patient had been receiving warfarin for 2 weeks and olanzapine for 6 days. On the eighth day after initiation of olanzapine, erythematous skin lesions developed on dependent areas. The international normalized ratio for warfarin was within the acceptable range; however, because warfarin has been associated with subcutaneous bleeding presenting as petechiae and ecchymosis, subcutaneous enoxaparin was substituted for warfarin. The skin lesions continued to worsen over the next week and developed into palpable lesions. Biopsy of the rash revealed leukocytoclastic vasculitis. In the absence of another cause, olanzapine was discontinued and the rash improved significantly. When the agitation recurred, risperidone was initiated, but the patient experienced dizziness with this agent. Olanzapine was resumed and the skin lesions recurred. Olanzapine was then changed to quetiapine, and the skin lesions improved over the next few weeks.

DISCUSSION

Olanzapine is commonly used in elderly patients to control behavioral disturbances associated with dementia, delirium, and other psychiatric disorders. Leukocytoclastic vasculitis is an infrequently reported adverse drug reaction with olanzapine. Its exact pathogenic mechanism is unknown, but both cell-mediated and humoral immunity appear to play important roles. Because drug-induced vasculitis has an identical clinical presentation and identical serologic/pathologic parameters to idiopathic forms of vasculitis, a high index of suspicion is necessary for its accurate diagnosis.

CONCLUSIONS

Because adverse drug reactions are common in elderly patients taking multiple medications, physicians should be vigilant when starting new medications and should attempt to eliminate unnecessary medications. Clinicians should be aware of the potential for leukocytoclastic vasculitis in association with olanzapine.