Cell-mediated immunity in allopurinol-induced hypersensitivity

The allopurinol metabolite, oxypurinol, drives oligoclonal expansions of drug-reactive T cells in resolved hypersensitivity cases and drug-naïve healthy donors

Allopurinol (ALP) is a successful drug used in the treatment of gout. However, this drug has been implicated in hypersensitivity reactions that can cause severe to life-threatening reactions such as Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). Individuals who carry the human leukocyte antigen (HLA)-B*58:01 allotype are at higher risk of experiencing a hypersensitivity reaction (odds ratios ranging from 5.62 to 580.3 for mild to severe reactions, respectively). In addition to the parent drug, the metabolite oxypurinol (OXP) is implicated in triggering T cell-mediated immunopathology via a labile interaction with HLA-B*58:01. To date, there has been limited information regarding the T-cell receptor (TCR) repertoire usage of reactive T cells in patients with ALP-induced SJS or TEN and, in particular, there are no reports examining paired αβTCRs. Here, using in vitro drug-treated PBMCs isolated from both resolved ALP-induced SJS/TEN cases and drug-naïve healthy donors, we show that OXP is the driver of CD8+ T cell-mediated responses and that drug-exposed memory T cells can exhibit a proinflammatory immunophenotype similar to T cells described during active disease. Furthermore, this response supported the pharmacological interaction with immune receptors (p-i) concept by showcasing (i) the labile metabolite interaction with peptide/HLA complexes, (ii) immunogenic complex formation at the cell surface, and (iii) lack of requirement for antigen processing to elicit drug-induced T cell responsiveness. Examination of paired OXP-induced αβTCR repertoires highlighted an oligoclonal and private clonotypic profile in both resolved ALP-induced SJS/TEN cases and drug-naïve healthy donors.

The Role of Patch Testing in Evaluating Delayed Hypersensitivity Reactions to Medications

Confirming drug imputability is an important step in the management of cutaneous adverse drug reactions (CADR). Re-challenge is inconvenient and in many cases life threatening. We review the literature on ideal patch testing technique for specific CADRs. Testing should be performed approximately 3 months after the resolution of the eruption using standard patch testing techniques. Commercially available patch test preparations are available for a minority of drugs, so in most cases, testing should be performed with the drug at various recommended concentrations and in different vehicles. Testing to all known excipients, such as dyes, vehicles and preservatives is also important. Immunosuppressive medications should be discontinued or down titrated to the lowest tolerable dose to decrease the risk of false negative reactions. We provide an overview of expert recommendations and extant evidence on the utility of patch testing for identifying the culprit drug in common CADRs and for specific drug or drug classes. Overall, there appears to be significant variability in the patch test positivity of different drugs, which is likely the result of factors intrinsic to the drug such as dermal absorption (as a function of lipophilicity and molecular size) and whether the drug itself or a downstream metabolite is implicated in the immune reaction. Drugs with high patch test positivity rates include beta-lactam antibiotics, aromatic anticonvulsants, phenytoin, and corticosteroids, among others. Patch testing positivity varies both as a function of the drug and type of CADR. The sum of the evidence suggests that patch testing in the setting of morbilliform eruptions, fixed drug eruption, acute generalized exanthematous pustulosis, and possibly also drug-induced hypersensitivity syndrome, photoallergic and eczematous reactions may be worthwhile, although utility of testing may vary on the specific drug in question for the eruption. It appears to be of limited utility and is not recommended in the setting of other complex CADR, such as SJS/TEN and leukocytoclastic vasculitis.

Erosive cheilitis as an early manifestation in DRESS syndrome

Drug reaction with eosinophilia and systemic symptoms (DRESS) is a distinct part of severe cutaneous adverse reactions (SCARs). It is characterized by fever, rash, hematologic abnormalities, lymphadenopathy, or/and different degrees of visceral organ involvement. Its diagnosis is particularly challenging due to the variability of its clinical presentations and its long latency period (2-6 weeks). Allopurinol, an uric acid-lowering drug, has been incriminated in several cases of allopurinol-induced DRESS syndrome. Through this paper, we present a case of allopurinol-induced DRESS syndrome with initial oral mucosal involvement. A 69-year-old female patient presented with an erosive cheilitis that started 1 week prior to his presentation. The cheilitis was associated with maculopapular rash and fever. She started taking allopurinol, as treatment of Gout, 6 weeks before hospitalization. The histologic findings obtained from skin biopsy were consistent with a toxic drug reaction. A complete blood count (CBC) showed a moderate eosinophilia. Alteration of renal function was also noted, and the diagnosis of allopurinol-induced DRESS syndrome was made. Systemic corticosteroid therapy was therefore started. The patient completely recovered and had been healthy for 3 years before developing a recurrence after re-challenge with allopurinol.

An Update on the Immunological, Metabolic and Genetic Mechanisms in Drug Hypersensitivity Reactions

Drug hypersensitivity reactions (DHRs) represent a major burden on the healthcare system since their diagnostic and management are complex. As they can be influenced by individual genetic background, it is conceivable that the identification of variants in genes potentially involved could be used in genetic testing for the prevention of adverse effects during drug administration. Most genetic studies on severe DHRs have documented HLA alleles as risk factors and some mechanistic models support these associations, which try to shed light on the interaction between drugs and the immune system during lymphocyte presentation. In this sense, drugs are small molecules that behave as haptens, and currently three hypotheses try to explain how they interact with the immune system to induce DHRs: the hapten hypothesis, the direct pharmacological interaction of drugs with immune receptors hypothesis (p-i concept), and the altered self-peptide repertoire hypothesis. The interaction will depend on the nature of the drug and its reactivity, the metabolites generated and the specific HLA alleles. However, there is still a need of a better understanding of the different aspects related to the immunological mechanism, the drug determinants that are finally presented as well as the genetic factors for increasing the risk of suffering DHRs. Most available information on the predictive capacity of genetic testing refers to abacavir hypersensitivity and anticonvulsants-induced severe cutaneous reactions. Better understanding of the underlying mechanisms of DHRs will help us to identify the drugs likely to induce DHRs and to manage patients at risk.

Allopurinol-Induced Stevens-Johnson Syndrome

Allopurinol is a first line agent in treating gout, but it also carries the risk of severe side effects. Stevens-Johnson syndrome (SJS) is one of the life threatening severe cutaneous adverse reactions caused by allopurinol. The severity of the severe cutaneous adverse reactions can be categorized based upon the area of skin involvement: (1) erythema multiforme major limited to 1-2 % of the body surface area (BSA); (2) SJS involving <10% of the BSA, (3) SJS and toxic epidermal necrolysis overlap involving 10-30% of the BSA and (4) toxic epidermal necrolysis syndrome involving >30% of the BSA. SJS can be caused by drugs and viruses, the former being more frequent. We report a case of an 85-year-old Han-Chinese female who developed SJS after ingestion of allopurinol 8 days prior to the hospitalization. The patient also had concomitant acute viral illness, which complicated the clinical scenario causing acute renal failure and hemodynamic compromise.

PSORS1C1 Hypomethylation Is Associated with Allopurinol-Induced Severe Cutaneous Adverse Reactions during Disease Onset Period: A Multicenter Retrospective Case-Control Clinical Study in Han Chinese

Background: Allopurinol-induced severe cutaneous adverse reactions (SCARs), including drug rash with eosinophilia and systemic symptoms (DRESS), Stevens-Johnson syndrome (SJS) and toxic epidermal necrosis (TEN), are life-threatening autoimmune reactions. Evidence is growing that epigenetic variation, particularly DNA methylation, is associated with autoimmune diseases. However, the potential role of aberrant DNA methylation in allopurinol-SCARs is largely unknown.

Objective: To address the knowledge gap between allopurinol-SCARs and DNA methylation, we studied the DNA methylation profiles in peripheral blood cells from allopurinol-SCARs and allopurinol-tolerant subjects.

Methods: A genome-scale DNA methylation profiling was conducted using the Illumina Infinium HumanMethylation450 (HM450) platform on 15 patients with allopurinol-SCARs (3 TEN, 2 SJS/TEN overlap and 10 SJS) and 20 age- and gender-matched allopurinol-tolerant controls at disease onset. Pyrosequencing was used to validate the candidate CpG (cytosine-guanine dinucleotide) sites in an independent cohort of 40 allopurinol-SCARs and 48 allopurinol-tolerants.

Results: After bioinformatics analysis of methylation data obtained from HM450 BeadChip, we identified 41 differentially methylated CpG loci (P < 0.05) annotated to 26 genes showing altered DNA methylation between allopurinol-SCARs and allopurinol-tolerants. Among these genes, significant hypomethylation of PSORS1C1 (cg24926791) was further validated in a larger sample cohort, showing significant difference between DRESS and controls (P = 0.00127), ST (SJS and TEN) and controls (P = 3.75 × 10⁻¹³), and SCARs and controls (P = 5.93 × 10⁻¹⁵).

Conclusions: Our data identified differentially methylated genes between allopurinol-SCARs and allopurinol-tolerant controls and showed that PSORS1C1 hypomethylation was associated with allopurinol-SCARs (OR = 30.22, 95%CI = 4.73–192.96) during disease onset, suggesting that aberrant DNA methylation may be a mechanism of allopurinol-SCARs.

Limitations: Firstly, the data come from whole blood samples known to possess epigenetic heterogeneity, i. e., blood samples comprise a heterogeneous cell population with varying proportions of distinct cell-types with different DNA methylation patterns. Consequently, the interpretation of DNA methylation results should be performed with great caution due to the heterogeneous nature of the sample. Secondly, whether the identified disease-associated changes of epigenome precede disease onset, or result from the disease progression, needs further investigation. Comparing the methylation status before patients develop allopurinol-SCARs and after may help examine methylation levels from disease onset to disease progression.

Drug Reaction, Eosinophilia and Systemic Symptoms (DRESS) syndrome secondary to allopurinol with early lymphadenopathy and symptom relapse

Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is a rare condition with a mortality rate of up to 10%. Herein, we describe a case of DRESS syndrome secondary to allopurinol and which may have been precipitated by amoxicillin, the diagnostic challenge it represented and the successful treatment of the condition with corticosteroids.

Drug Reaction, Eosinophilia and Systemic Symptoms (DRESS) syndrome secondary to allopurinol with early lymphadenopathy and symptom relapse

Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is a rare condition with a mortality rate of up to 10%. Herein, we describe a case of DRESS syndrome secondary to allopurinol and which may have been precipitated by amoxicillin, the diagnostic challenge it represented and the successful treatment of the condition with corticosteroids.

Allopurinol hypersensitivity: investigating the cause and minimizing the risk

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

Oxypurinol-Specific T Cells Possess Preferential TCR Clonotypes and Express Granulysin in Allopurinol-Induced Severe Cutaneous Adverse Reactions

Allopurinol, a first-line drug for treating gout and hyperuricemia, is one of the leading causes of severe cutaneous adverse reactions (SCARs). To investigate the molecular mechanism of allopurinol-induced SCAR, we enrolled 21 patients (13 Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN) and 8 drug reaction with eosinophilia and systemic symptoms (DRESS)), 11 tolerant controls, and 23 healthy donors. We performed in vitro T-cell activation assays by culturing peripheral blood mononuclear cells (PBMCs) with allopurinol, oxypurinol, or febuxostat and measuring the expression of granulysin and IFN-γ in the supernatants of cultures. TCR repertoire was investigated by next-generation sequencing. Oxypurinol stimulation resulted in a significant increase in granulysin in the cultures of blood samples from SCAR patients (n=14) but not tolerant controls (n=11) or healthy donors (n=23). Oxypurinol induced T-cell response in a concentration- and time-dependent manner, whereas allopurinol or febuxostat did not. T cells from patients with allopurinol-SCAR showed no crossreactivity with febuxostat. Preferential TCR-V-β usage and clonal expansion of specific CDR3 (third complementarity-determining region) were found in the blister cells from skin lesions (n=8) and oxypurinol-activated T-cell cultures (n=4) from patients with allopurinol-SCAR. These data suggest that, in addition to HLA-B*58:01, clonotype-specific T cells expressing granulysin upon oxypurinol induction participate in the pathogenesis of allopurinol-induced SCAR.

T cell-mediated hypersensitivity reactions to drugs

The immunological mechanisms driving delayed hypersensitivity reactions (HSRs) to drugs mediated by drug-reactive T lymphocytes are exemplified by several key examples and their human leukocyte antigen (HLA) associations: abacavir and HLA-B*57:01, carbamazepine and HLA-B*15:02, allo-purinol and HLA-B*58:01, and both amoxicillin-clavulanate and nevirapine with multiple class I and II alleles. For HLA-restricted drug HSRs, specific class I and/or II HLA alleles are necessary but not sufficient for tissue specificity and the clinical syndrome. Several models have been proposed to explain the immunopathogenesis of severe T cell-mediated drug HSRs, and our increased understanding of the risk factors and mechanisms involved in the development of these reactions will further the development of sensitive and specific strategies for preclinical screening that will lead to safer and more cost-effective drug design.

Allopurinol induced erythroderma

Allopurinol, a widely prescribed urate lowering agent is responsible for various adverse drug reactions, including erythroderma. A 45-year-old male patient was admitted with the complaints of fever, redness and scaling all over the body after 3-4 weeks of allopurinol treatment for asymptomatic hyperuricemia. Elevated liver enzymes were detected in his blood analysis. Skin biopsy was consistent with drug induced erythroderma. Allopurinol was stopped and steroids were started. Patient improved over a period of 2 weeks.

Allopurinol-induced DRESS syndrome mimicking biliary obstruction

An 84-year-old man was admitted to our hospital with fever, jaundice, and itching. He had been diagnosed previously with chronic renal failure and diabetes, and had been taking allopurinol medication for 2 months. A physical examination revealed that he had a fever (38.8℃), jaundice, and a generalized maculopapular rash. Azotemia, eosinophilia, atypical lymphocytosis, elevation of liver enzymes, and hyperbilirubinemia were detected by blood analysis. Magnetic resonance cholangiography revealed multiple cysts similar to choledochal cysts in the liver along the biliary tree. Obstructive jaundice was suspected clinically, and so an endoscopic ultrasound examination was performed, which ruled out a diagnosis of obstructive jaundice. The patient was diagnosed with DRESS (Drug Rash with Eosinophilia and Systemic Symptoms) syndrome due to allopurinol. Allopurinol treatment was stopped and steroid treatment was started. The patient died from cardiac arrest on day 15 following admission.

Detection of HLA-B*58:01, the susceptible allele for allopurinol-induced hypersensitivity, by loop-mediated isothermal amplification

BACKGROUND

Allopurinol, a common medication for gout treatment, can cause rare but life-threatening severe cutaneous adverse reactions. A strong pharmacogenetic association of human leucocyte antigen (HLA)-B*58:01 with allopurinol-induced drug hypersensitivity has been reported, especially in the Han Chinese population.

OBJECTIVES

To develop a rapid and simple loop-mediated isothermal amplification (LAMP) assay of HLA-B*58:01 and evaluate its feasibility in predicting allopurinol-induced drug hypersensitivity.

METHODS

Two sets of LAMP primers targeting exons 2 and 3 of HLA-B*58:01 were designed. DNA extracted from 20 clinical blood samples of patients with gout was used to evaluate the effectiveness of the two LAMP primer sets for the detection of HLA-B*58:01.

RESULTS

The results were compared with routine clinical genotyping methods. All extracted DNA samples tested with the HLA-B*58:01 LAMP assay showed agreement with the routine genotyping results. No amplifications were observed when unextracted blood samples were tested.

CONCLUSIONS

The HLA-B*58:01 LAMP assay was confirmed to be simple, rapid and specific for the detection of HLA-B*58:01, and therefore of potential value in the diagnosis of allopurinol-induced hypersensitivity.

Successful use of allopurinol in a patient on dialysis

We report the case of a man with chronic tophaceous gout who had end-stage renal failure secondary to the Alport syndrome. Following a failed kidney transplant, where urate deposition was a suspected contributor, the patient responded positively to consistent allopurinol therapy and regular haemodialysis sessions. Extensive and destructive tophi receded in size remarkably and the almost constant incidence of acute attacks of gout subsided. The patient has recently received a new kidney transplant and his plasma concentrations of urate are controlled well with allopurinol and he no longer experiences acute attacks of gout. While efficacious, adherence is critical for achieving the therapeutic effects of allopurinol even in end-stage renal disease.

Cutaneous adverse drug reactions to allopurinol: 10 year observational survey of the dermatology department--Cagliari University (Italy)

BACKGROUND

Allopurinol is extensively prescribed for conditions associated with urate excess, despite being responsible for severe cutaneous adverse drug reactions (ADR).

OBJECTIVE

A cross-sectional survey of allopurinol cases observed at the main Dermatology Department with inpatients facilities in southern Sardinia. (approx 560,836 inhabitants).

MATERIAL AND METHODS

Data collection of all consecutive patients referred for ADR between 2001 and 2010. Causality assessment followed the WHO Collaborating Centre for Drug Monitoring criteria; illness severity score was adopted for toxic epidermal necrolysis (SCORTEN).

RESULTS

Allopurinol was the culprit drug in 84 of 780 cutaneous ADR cases (10.7%; 8.4 cases/year). Mean age was 74 years, 58% of the patients were female, 95% of patients required hospitalization. Clinical forms were maculo-papular eruptions (34 cases), Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis (31 cases), vasculitis (six cases), Drug Rash Eosinophilia and Systemic Symptoms (DRESS) (three cases), Acute Generalized Exanthematous Pustolosis (AGEP) (three cases), Pityriasis rosea-like eruption (three cases), lichenoid dermatitis (two cases), fixed drug eruption (one case), erythroderma (one case). The indication for allopurinol prescription was asymptomatic hyper-uricemia in 95% of the patients. Twelve patients were under allopurinol dosage adjustment according to creatinine clearance. Final causality assessment was definite for 12% of the cases and probable for the remaining 88%. Full recovery was achieved in 88% of subjects; ten SJS/TEN patients died (12% overall mortality; 32% mortality of the SJS/TEN cases).

CONCLUSION

Considering the populations size of Southern Sardinia, is plausible that 1.5/100,000 Sardinian will be affected by allopurinol related ADR per year. Advanced age, and inappropriate allopurinol prescription were the main conditions affecting morbidity and mortality.

Patch testing in fixed drug eruptions--a 20-year review

BACKGROUND

The fixed drug eruption is a common adverse drug reaction. Clear identification of the culprit drug is not always possible in the clinical setting, and oral rechallenge may induce new lesions or severe reactions.

OBJECTIVES

The main purpose of this study was to evaluate the diagnostic value of patch testing in establishing an aetiological diagnosis in fixed drug eruptions.

METHOD

A retrospective analysis was conducted evaluating 52 patients (17M/35F, mean age 53±17 years) with clinical diagnoses of fixed drug eruptions submitted to patch tests in a 20-year period in a Dermatology Department. Nonsteroidal anti-inflammatory drugs (NSAID) were clinically suspected in 90.4% of the cases, followed by antibiotics (28.9%) and paracetamol (15.4%).

RESULTS

Patch tests on pigmented lesions were reactive in 21 patients (40.4%), 20 of those to NSAID (nimesulide, piroxicam and etoricoxib) and 1 to an antihistamine (cetirizine). All patch tests using other drugs were negative, even under conditions of high clinical suspicion. Oral rechallenge allowed confirmation of drug imputability in 5 of 31 test-negative cases. Cross reactivity was frequently observed between piroxicam and other oxicams, and between different antihistamines.

CONCLUSIONS

Patch testing was shown to be a simple and safe method to confirm drug imputabililty in fixed drug eruption, mainly when NSAID or multiple drugs are suspected. Persistent lack of reactivity to drug classes such as antibiotics and allopurinol represent an important limitation.

Clinical pharmacokinetics and pharmacodynamics of allopurinol and oxypurinol

Allopurinol is the drug most widely used to lower the blood concentrations of urate and, therefore, to decrease the number of repeated attacks of gout. Allopurinol is rapidly and extensively metabolised to oxypurinol (oxipurinol), and the hypouricaemic efficacy of allopurinol is due very largely to this metabolite. The pharmacokinetic parameters of allopurinol after oral dosage include oral bioavailability of 79 +/- 20% (mean +/- SD), an elimination half-life (t((1/2))) of 1.2 +/- 0.3 hours, apparent oral clearance (CL/F) of 15.8 +/- 5.2 mL/min/kg and an apparent volume of distribution after oral administration (V(d)/F) of 1.31 +/- 0.41 L/kg. Assuming that 90 mg of oxypurinol is formed from every 100mg of allopurinol, the pharmacokinetic parameters of oxypurinol in subjects with normal renal function are a t((1/2)) of 23.3 +/- 6.0 hours, CL/F of 0.31 +/- 0.07 mL/min/kg, V(d)/F of 0.59 +/- 0.16 L/kg, and renal clearance (CL(R)) relative to creatinine clearance of 0.19 +/- 0.06. Oxypurinol is cleared almost entirely by urinary excretion and, for many years, it has been recommended that the dosage of allopurinol should be reduced in renal impairment. A reduced initial target dosage in renal impairment is still reasonable, but recent data on the toxicity of allopurinol indicate that the dosage may be increased above the present guidelines if the reduction in plasma urate concentrations is inadequate. Measurement of plasma concentrations of oxypurinol in selected patients, particularly those with renal impairment, may help to decrease the risk of toxicity and improve the hypouricaemic response. Monitoring of plasma concentrations of oxypurinol should also help to identify patients with poor adherence. Uricosuric drugs, such as probenecid, have potentially opposing effects on the hypouricaemic efficacy of allopurinol. Their uricosuric effect lowers the plasma concentrations of urate; however, they increase the CL(R) of oxypurinol, thus potentially decreasing the influence of allopurinol. The net effect is an increased degree of hypouricaemia, but the interaction is probably limited to patients with normal renal function or only moderate impairment.

Hypersensitivity Syndrome and Pure Red Cell Aplasia Following Allopurinol Therapy in a Patient with Chronic Kidney Disease

OBJECTIVE:

To report a rare case of combined hypersensitivity syndrome and pure red cell aplasia (PRCA) following allopurinol therapy.

CASE SUMMARY:

A 43-year-old woman with underlying mesangioproliferative glomerulonephritis developed fever, generalized morbilliform rash, leukocytosis with marked eosinophilia, and hepatic dysfunction 3 weeks after starting allopurinol therapy (300 mg/day for 3 days followed by 200 mg/day) for hyperuricemia and arthritis. The clinical findings were judged to be a probable drug reaction according to the Naranjo probability scale. The drug-induced hypersensitivity syndrome (DHS) resolved after withdrawal of allopurinol and initiation of systemic corticosteroid therapy. However, there was progressive worsening of anemia with reticulocytopenia; PRCA was suspected. PRCA was judged to be a possible drug reaction according to the Naranjo probability scale. The patient refused blood transfusion and bone marrow biopsy. Recombinant human erythropoietin was initiated in addition to prednisolone 15 mg daily. Eleven days later (~7 wk after allopurinol withdrawal), both the hemoglobin level and reticulocyte count began to rise. The patient consented to a bone marrow study at that time, which confirmed the presence of dysplasia involving only the erythroid lineage.

DISCUSSION:

Allopurinol may induce DHS, aplastic anemia, and, in rare instances, PRCA. We report the first case of PRCA concurrent with allopurinol-induced DHS in a patient with chronic kidney disease. Discontinuation of allopurinol is the first step in the treatment of such cases. The slow recovery of PRCA might be partly attributed to her underlying chronic kidney disease.

CONCLUSIONS:

To minimize serious DHS, proper indications for treatment and dosage adjustment should be closely observed when starting allopurinol therapy in patients with chronic kidney disease.

Allopurinol-induced Severe Hypersensitivity with Acute Renal Failure

A 62-year-old male was sent to the emergency room due to a high fever and generalized skin rash after taking allopurinol for 9 days. Physical examination was normal except for the generalized skin rash presenting with erythematous macules. Complete blood count showed leukocytosis with eosinophilia. Blood biochemistry showed impaired renal and hepatic function. Pathologic examination concluded that the skin rash was erythema multiforme. These findings met the diagnostic criteria for allopurinol-induced hypersensitivity syndrome (AHS). Our patient not only had the most common skin lesion but soon developed acute renal failure that required intermittent hemodialysis, despite rapid discontinuation of allopurinol and adequate hydration and steroid therapy. No other causes of acute renal failure were found. Renal impairment was the worst part of the patient's condition and he never completely recovered. AHS should be considered in the differential diagnosis of acute renal and hepatic failure in patients with evidence of allergy and recent use of allopurinol.

HLA-B*5801 allele as a genetic marker for severe cutaneous adverse reactions caused by allopurinol

Allopurinol, a commonly prescribed medication for gout and hyperuricemia, is a frequent cause of severe cutaneous adverse reactions (SCAR), which include the drug hypersensitivity syndrome, Stevens-Johnson syndrome, and toxic epidermal necrolysis. The adverse events are unpredictable and carry significant morbidity and mortality. To identify genetic markers for allopurinol-SCAR, we carried out a case-control association study. We enrolled 51 patients with allopurinol-SCAR and 228 control individuals (135 allopurinol-tolerant subjects and 93 healthy subjects from the general population), and genotyped for 823 SNPs in genes related to drug metabolism and immune response. The initial screen revealed strong association between allopurinol-SCAR and SNPs in the MHC region, including BAT3 (encoding HLA-B associated transcript 3), MSH5 (mutS homolog 5), and MICB (MHC class I polypeptide-related sequence B) (P < 10(-7)). We then determined the alleles of HLA loci A, B, C, and DRB1. The HLA-B*5801 allele was present in all (100%) 51 patients with allopurinol-SCAR, but only in 20 (15%) of 135 tolerant patients [odds ratio 580.3 (95% confidence interval, 34.4-9780.9); corrected P value = 4.7 x 10(-24)] and in 19 (20%) of 93 of healthy subjects [393.51 (23.23-6665.26); corrected P value = 8.1 x 10(-18)]. HLA alleles A*3303, Cw*0302, and DRB1*0301 were in linkage disequilibrium and formed an extended haplotype with HLA-B*5801. Our results indicated that allopurinol-SCAR is strongly associated with a genetic predisposition in Han Chinese. In particular, HLA-B*5801 allele is an important genetic risk factor for this life-threatening condition.

Intravenous desensitization to allopurinol in a heart transplant patient with gout

BACKGROUND

Oral desensitization with allopurinol presents a problem for patients with allopurinol hypersensitivity and gout that needs to be controlled rapidly. To our knowledge, only 1 case report of intravenous (i.v.) desensitization has been previously published.

OBJECTIVE

To present a case report of a patient with cutaneous reactions to allopurinol who underwent i.v. allopurinol desensitization.

METHODS

Intravenous infusion of allopurinol was performed using an escalating, 19-dose protocol.

RESULTS

No adverse reactions were precipitated by 2 i.v., escalating dose procedures, allowing continuation of effective treatment of the patient's hyperuricemia.

CONCLUSIONS

This case of safe and effective desensitization with allopurinol by the i.v. route should emphasize the need for a trial of this protocol in additional patients in whom rapid desensitization would be advantageous.

Mechanisms in cutaneous drug hypersensitivity reactions

Up to 3% of all hospital admissions are due to adverse drug reactions (ADRs), and between 10% and 20% of hospital inpatients develop ADRs. Individual susceptibility to becoming 'sensitized' or allergic to a drug is thought to result from altered metabolic handling of the drug. Reactive intermediate compounds form haptens, bind to proteins and induce immune responses. Depending on whether the immune system generates antibodies or sensitized T cells, different clinical patterns of hypersensitivity may result. At present, both in vivo or in vitro tests to identify the culprit drug or to confirm the presence of hypersensitivity are not widely used because they are either not generally robust or not readily accessible. In vitro tests require the true immunogen/antigen to detect antibodies or sensitized T cells. As the metabolic basis underlying susceptibility to adverse drug reactions is elucidated, the resolution of immunological mechanisms and development of reliable tests will ensue. This will also become of great value for prediction of individuals at risk of becoming sensitized by a particular drug.

Liver and kidney diseases

The spectrum of renal disease in patients with liver disease is expanding. The recognition of renal complications of liver diseases is essential in the management of these patients. As liver transplantation is a treatment option for many patients with chronic liver disease, the presence of renal complications impacts the decision regarding transplantation and influences the course of these patients after transplantation, especially with regard to the use of immunosuppressive therapy. The involvement of the liver and kidney in systemic conditions is common and adds to the morbidity and mortality of patients.

Difficult gout and new approaches for control of hyperuricemia in the allopurinol-allergic patient

A major obstacle to the treatment of hyperuricemia in patients allergic to allopurinol is the limited availability of suitable, equally effective, alternative, urate-lowering drugs. Conventional uricosuric drugs, including probenecid and sulfinpyrazone, are recommended for allopurinol- intolerant patients with gout and "underexcretion" hyperuricemia who have normal renal function and no history of nephrolithiasis. Therapeutic options in those in whom traditional uricosuric drugs are contraindicated, ineffective, or poorly tolerated include slow oral desensitization to allopurinol and cautious administration of oxipurinol. Allopurinol desensitization is useful particularly in those who have failed other treatment modalities. If available (as in Europe, South Africa, and Japan), benzbromarone may be tried in patients with gout and mild-to-moderate renal insufficiency. Recombinant urate oxidase can be used in the short-term prophylaxis and treatment of chemotherapy- associated hyperuricemia in patients with lymphoproliferative and myeloproliferative disorders. Hyperuricemia and gout occur with increased frequency in cyclosporine-treated allograft transplant recipients. The management of gout in these patients is complicated by two main factors: cyclosporine-induced renal impairment, and interactions with medications used to preserve the allograft.

Efficacy and safety of desensitization to allopurinol following cutaneous reactions

OBJECTIVE

To evaluate the long-term efficacy and safety of slow oral desensitization in the management of patients with hyperuricemia and allopurinol-induced maculopapular eruptions.

METHODS

A retrospective evaluation of an oral desensitization regimen using gradual dosage-escalation of allopurinol in 32 patients (30 with gout and 2 with chronic lymphocytic leukemia) whose therapy was interrupted because of a pruritic cutaneous reaction to the drug.

RESULTS

Twenty-one men and 11 women with a mean age of 63 years (range 17-83 years), a mean serum urate level of 618 micromoles/liter (range 495-750) (or, mean 10.4 mg/dl [range 8.3-12.6]), and a mean serum creatinine level of 249 micromoles/liter (range 75-753) (or, mean 2.8 mg/dl [range 0.8-8.5]) were studied. Desensitization failed in 4 patients because of unmanageable recurrent rash. Twenty-eight patients completed the desensitization procedure to a target allopurinol dosage of 50-100 mg/day, 21 without deviation from the protocol for a mean of 30.5 days (range 21-56 days) and 7 requiring dosage adjustments because of a recurrent rash over 53.8 days (range 40-189 days). Seven of these 28 patients developed late cutaneous reactions 1-20 months postdesensitization, 4 responding to dosage modification and 3 discontinuing the drug. Twenty-five of the 32 patients (78%) continued to take allopurinol; their mean duration of followup was 32.6 months (range 3-92 months) and the mean postdesensitization serum urate level was 318 micromoles/liter (range 187-452) (or, mean 5.3 mg/dl [range 3.0-7.5]).

CONCLUSION

The study confirms the long-term efficacy and safety of slow oral desensitization to allopurinol in patients with maculopapular eruptions, particularly in those with gout, who cannot be treated with uricosurics or other urate-lowering drugs. Although pruritic skin eruptions may recur both during and after desensitization, most of these cutaneous reactions can be managed by temporary withdrawal of allopurinol and dosage adjustment.

The effects of allopurinol on immune function in normal BALB/c and SCID mice

To clarify the relationship between purine metabolism and immunity, the in vivo immunosuppressive effects of allopurinol (AL), a xanthinoxidase (XO) inhibitor, were studied using normal BALB/c and severe combined immunodeficient (SCID) mice. Following AL administration for 14 weeks (long term), a decreased immune response to ovalbumin (OVA) in the peripheral blood was observed in normal mice, which might not be only due to direct B cell suppression but also due to suppression of helper T cell function. In the SCID mice, there was a markedly late and reduced recovery of surface immunoglobulin (sIg) positive cells, which are markers for mature B lymphocytes, in the peripheral blood after AL administration. The total immunoglobulin G (IgG) titers in the AL treated group were significantly lower than in the control group 6 weeks after stem cell transfer, but increased until there was no difference in the titers between the two groups at week 14. CD4 positive helper T cells and CD8 positive T cells were slow to recover, though these gradually recovered to reach normal levels in the mature stage. These data suggest that the administration of AL may modulate B cell and T cell responses in OVA-immunized antibody formation. Furthermore, this study showed that AL could influence immune functions during the pre-natal and developmental periods and that its effects might differ according to the stages of maturity of the immune cells.

Allopurinol hypersensitivity syndrome: hypersensitivity to oxypurinol but not allopurinol

Allopurinol is a xanthine oxidase inhibitor widely used to control plasma uric acid levels. Episodes of hypersensitivity to the drug are not rare. A severe form of this with a generalized exanthem, fever and liver involvement has been termed the allopurinol hypersensitivity syndrome (AHS). Patch testing and lymphocyte stimulation testing (LST) are not helpful in confirming this sensitivity. Allopurinol works as a substrate of xanthine oxidase, and is rapidly oxidized into oxypurinol in vivo. Therefore, the biological half-life of oxypurinol is markedly longer than that of allopurinol. In addition, conspicuous pre-existing renal impairment has been noted in many AHS patients. Thus, it is possible that AHS is a manifestation of hypersensitivity to oxy-, not allopurinol. Here, we now report three cases of AHS in which there were significant lymphoproliferative reactions to oxypurinol but not allopurinol.