Laboratory features and pharmacological management of early and late-onset primary Sjögren's syndrome

BACKGROUND

Primary Sjögren's Syndrome (pSS) is a systemic chronic autoimmune disorder that contributes to dry mouth (xerostomia) and eyes (xerophthalmia). It mainly affects females between 40 and 60 years old. So far, there is no treatment to cure SS; however, there is a list of medications that can ameliorate the symptoms. In addition, there has been no single test until now to detect pSS, but clinical and immunological investigations are applied as diagnostic tools. Therefore, this study aimed to explore the characteristics of pSS in Saudi patients based on the onset of the disease through laboratory findings and pharmaceutical management.

METHODOLOGY

This retrospective study examined diagnosed patients with pSS between 2018 and 2023 from the National Guard Hospital, Saudi Arabia. Data of pSS patients was categorized into two groups: early (under 40 years old) and late-onset (40 years old and above). Data on demographic information, mortality rate, and blood tests such as complete blood count (CBC), creatinine, erythrocyte sedimentation rate (ESR), and vitamin levels, in addition to prescribed medications, were collected from the patient's medical record. Chi-square and t-tests were mainly used, and statistical significance was determined at a P-value less than 0.05.

RESULTS

A total of 453 patients were included in the study, where the early-onset group comprised 136 and the late-onset group comprised 317 patients. The mean age of the early and late onset was 34.2 and 60.4, respectively. ESR was significantly higher in the early (46.3 mm/hr) and late-onset (49.8 mm/hr). The most common medication used by all pSS patients was hydroxychloroquine. However, artificial tears were mainly observed in the late-onset group. Other medications, such as pilocarpine, methotrexate, and azathioprine, were prescribed to pSS patients to a lesser extent.

CONCLUSION

This study suggests that the onset of pSS could occur even before the age of 40 among Saudi citizens. Notably, elevated ESR levels appeared to be a feature of pSS, which was consistent with other previous findings. The variability of some medications between early-onset and late-onset pSS may indicate disease progression. However, further investigations are required to confirm this observation.

Thiopurine S-Methyltransferase Polymorphisms Predict Hepatotoxicity in Azathioprine-Treated Patients with Autoimmune Diseases

Thiopurine methyltransferase (TPMT) is the rate-limiting enzyme in Azathioprine (AZA) metabolization. Although studies have discussed the association between the TPMT polymorphisms and myelosuppression, the data about the relationship between TPMT genotypes and hepatoxicity in Asian patients remain limited. This study investigated the correlation between TPMT polymorphisms and AZA-related hepatotoxicity. This study enrolled the patients who had prior exposure to AZA from the Taichung Veterans General Hospital (TCVGH)-Taiwan Precision Medicine Initiative (TPMI) cohort. Genetic variants were determined using a single nucleotide polymorphism (SNP) array. Participants were accordingly categorized into normal metabolizer (NM) and non-normal metabolizer (non-NM) groups. From the TCVGH-TPMI cohort, we included 50 TPMT non-NM patients, including 1 poor metabolizer (PM), 49 intermediate metabolizers (IMs), and 1000 NM patients. The non-NM genotype was associated with hepatotoxicity compared with the NM genotype (hazard ratio (HR): 3.85, 95% confidence interval (CI): 1.83−8.10). In the non-NM group, the 3-year cumulative incidence of hepatotoxicity was higher than that in the NM group at 8.5% in the first year and 18.6% in the second and third years (p < 0.001). A TPMT non-NM genotype was associated with the occurrence of hepatotoxicity following AZA therapy. Preemptive testing helps individualize AZA therapy by minimizing the risk of hepatotoxicity.

Pharmacogenetics of Drug Therapies in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic systemic inflammatory disorder that can lead to severe joint damage and is often associated with a high morbidity and disability. Disease-modifying anti-rheumatic drugs (DMARDs) are the mainstay of treatment in RA. DMARDs not only relieve the clinical signs and symptoms of RA but also inhibit the radiographic progression of disease and reduce the effects of chronic systemic inflammation. Since the introduction of biologic DMARDs in the late 1990s, the therapeutic range of options for the management of RA has significantly expanded. However, patients' response to these agents is not uniform with considerable variability in both efficacy and toxicity. There are no reliable means of predicting an individual patient's response to a given DMARD prior to initiation of therapy. In this chapter, the current published literature on the pharmacogenetics of traditional DMARDS and the newer biologic DMARDs in RA is highlighted. Pharmacogenetics may help individualize drug therapy in patients with RA by providing reliable biomarkers to predict medication toxicity and efficacy.

Therapeutic drug monitoring of immunosuppressive drugs in hepatology and gastroenterology

Immunosuppressive drugs have been key to the success of liver transplantation and are essential components of the treatment of inflammatory bowel disease (IBD) and autoimmune hepatitis (AIH). For many but not all immunosuppressants, therapeutic drug monitoring (TDM) is recommended to guide therapy. In this article, the rationale and evidence for TDM of tacrolimus, mycophenolic acid, the mammalian target of rapamycin inhibitors, and azathioprine in liver transplantation, IBD, and AIH is reviewed. New developments, including algorithm-based/computer-assisted immunosuppressant dosing, measurement of immunosuppressants in alternative matrices for whole blood, and pharmacodynamic monitoring of these agents is discussed. It is expected that these novel techniques will be incorporate into the standard TDM in the next few years.

Azathioprine-induced pancytopenia with normal TPMT activity presenting with HSV oral ulcers

A 65-year-old man with treatment-resistant psoriatic arthritis, hypertension, dyslipidaemia and benign prostatic hyperplasia (BPH) presented with herpes simplex virus (HSV) oral ulcers and a recent 15 lb weight loss due to reduced consumption. Five weeks previously, his methotrexate was tapered and he had begun taking azathioprine. The patient's thiopurine S-methyltransferase (TPMT) activity level was normal prior to starting azathioprine. He was found to have pancytopenia with normal folate levels and azathioprine was discontinued. His pancytopenia worsened, with a nadir 8 days after stopping azathioprine, before returning to normal levels. His oral ulcers improved and he was able to tolerate solid food. This case illustrates that decreased TPMT activity is not the only risk factor for pancytopenia as an adverse reaction to azathioprine. Furthermore, HSV stomatitis may be the presenting symptom of pancytopenia. The timeline of improvement in cell counts illustrated in this patient has implications for the management of suspected azathioprine-induced pancytopenia.

NUDT15 R139C Variants Increase the Risk of Azathioprine-Induced Leukopenia in Chinese Autoimmune Patients

The aim of this study was to investigate the influence of NUDT15 R139C, thiopurine S-methyltransferase (TPMT), and 6-TGN on azathioprine (AZA) induced leukopenia in Chinese autoimmune patients. Among 87 enrolled patients, 23 (26.4%) had leukopenia. The NUDT15 R139C variant was associated with leukopenia (p = 1.86 × 10⁻⁷; OR: 7.59; 95% CI: 3.16–18.21). However, TPMT genotype was not shown to be correlated with the incidence of leukopenia (p = 0.95). There was no significant difference of 6-TGN concentration between patients with or without leukopenia (p = 0.15) and no association was found in patients with NUDT15 R139C variants alleles (p = 0.62). Finally, we found that the range of 6-TGN concentrations in autoimmune diseases was much lower than the established 6-TGN monitoring range for inflammatory bowel diseases. Therefore, the variant of NUDT15 R139C is strongly associated with AZA-induced leukopenia in Chinese patients with various autoimmune diseases such as systemic lupus erythematosus, Sjögren's syndrome, etc.

Role of Pharmacogenomics in Kidney Disease and Injury

There has been considerable excitement in the kidney community surrounding the research findings on the genetic contributions to kidney diseases. However, positive outcomes of personalized therapeutic interventions can be circumvented by unpredictable pharmacokinetics of prescribed drugs. Furthermore, unpredictable drug disposition can result in toxicities such as kidney injury. Patient covariates, disease covariates, and pharmacogenetics all contribute to variability in drug disposition. Further treatment personalization and avoidance of drug- and biologic- induced kidney injury will require extensive knowledge and expertise in renal clinical pharmacology. The current review will focus on the pharmacogenetics of drugs and biologics used in the treatment of glomerular kidney diseases and drugs implicated in inducing kidney injury phenotypes.

Pharmacogenetics in rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic inflammatory arthritis leading to severe joint damage and associated with high morbidity and mortality. Disease-modifying antirheumatic drugs (DMARDs) are the mainstay of treatment in RA. DMARDs not only relieve the clinical signs and symptoms of RA but also inhibit the radiographic progression of disease. In the last decade, a new class of disease-modifying medications, the biologic agents, has been added to the existing spectrum of DMARDs in RA. However, patients' response to these agents is not uniform with considerable variability in both efficacy and toxicity. There are no reliable means of predicting an individual patient's response to a given DMARD prior to initiation of therapy. In this chapter, the current published literature on the pharmacogenetics of traditional DMARDS and the newer biologic DMARDs in RA is highlighted. Pharmacogenetics may help individualize drug therapy in patients with RA in the near future.

Association of thiopurine methyltransferase status with azathioprine side effects in Chinese patients with systemic lupus erythematosus

Azathioprine (AZA) is indicated for the treatment of systemic lupus erythematosus (SLE). Thiopurine methyltransferase (TPMT) is the rate-limiting enzyme in the steps of AZA metabolization. Heritable deficiency of TPMT enzyme activity and polymorphisms may lead to leukopenia. This study aims to detect TPMT polymorphisms and TPMT enzyme activity in Chinese SLE patients and to describe the association between TPMT genotypes and adverse effects of AZA. One hundred and twenty-six SLE patients with present or previous thiopurine therapy were identified from a local database. Adverse effects were documented. No TPMT*2, TPMT*3A, or TPMT*3B mutant alleles were detected. TPMT*3C was detected in four patients (3.17 %). The heterozygotes had significantly lower mean TPMT activity as compared to the homozygotes (2.38 ± 1.24 vs. 12.56 ± 7.02 U/mL, P < 0.001). Twenty-seven cases (21.42 %) exhibited adverse effects. All of the heterozygotes (4/4, 100 %) developed severe leukopenia, and three cases (3/4, 75 %) of whom exhibited alopecia simultaneously. The specificity of TPMT*3C for predicting leukopenia and alopecia was 100 and 99.17 %, respectively, and the sensitivity was 28.57 and 60.00 %, respectively. The mean value of TPMT activity with leukopenia (4.67 ± 3.01 vs. 13.2 ± 6.94 U/mL RBC, P < 0.001) or alopecia (2.31 ± 1.16 vs. 12.65 ± 6.98 U/mL RBC, P < 0.001) was significantly lower than those without. TPMT*3C was the most common mutant polymorphism found in the study group. TPMT activity is reduced in TPMT*3C mutant. AZA-induced leukopenia and alopecia were partly correlated to TPMT*3C heterozygotes and low TPMT activity. The results of this study suggest that the value of TPMT genotyping before AZA therapy was limited in Chinese SLE patients, considering the low sensitivity. Routine monitoring of TPMT activity before prescribing and continuous hematological monitoring dose were recommended.

Successful azathioprine treatment with metabolite monitoring in a pediatric inflammatory bowel disease patient homozygous for TPMT*3C

Thiopurine S-methyltransferase (TPMT) methylates purine analogues, showing TPMT activity in inverse relation to concentrations of active metabolites such as 6-thioguanine nucleotide (6-TGN). With conventional dosing of thiopurines, patients with homozygous variant TPMT alleles consistently suffer from severe myelosuppression. Here, we report a patient with TPMT*3C/*3C who managed successfully with monitoring of thiopurine metabolites. The patient was an 18-year-old male diagnosed with Crohn's disease. The standard dose of azathioprine (AZA) (1.8 mg/kg/day) with mesalazine (55.6 mg/kg/day) was prescribed. Two weeks after starting AZA treatment, the patient developed leukopenia. The DNA sequence analysis of TPMT identified a homozygous missense variation (NM_000367.2: c.719A>G; p.Tyr240Cys), TPMT*3C/*3C. He was treated with adjusted doses of azathioprine (0.1-0.2 mg/kg/day) and his metabolites were closely monitored. Leukopenia did not reoccur during the follow-up period of 24 months. To our knowledge, this is the first case of a patient homozygous for TPMT*3C successfully treated with azathioprine in Korea. While a TPMT genotyping test may be helpful to determine a safe starting dose, it may not completely prevent myelosuppression. Monitoring metabolites as well as routine laboratory tests can contribute to assessing drug metabolism and optimizing drug dosing with minimized drug-induced toxicity.

Multiple cutaneous neutropenic ulcers associated with azathioprine

We report a case of neutropenic ulceration in a 42-year-old woman receiving azathioprine for pemphigus vulgaris. She developed multiple indolent ulcers involving the nose, neck, and back, after about 6–8 weeks following commencement of azathioprine 50 mg daily. The ulcers were large, disfiguring, dry, and with basal necrotic slough. They were painless and did not discharge pus. The absolute neutrophil count was severely depressed initially, but normalized following azathioprine withdrawal. Swab culture revealed colonization with Klebsiella pneumoniae and the ulcers healed with local debridement, treatment with imipenem, and topical application of mupirocin. However, nasal disfigurement persisted. Neutropenic ulceration is known to be associated with azathioprine therapy but we report this case because of the unusual presentation—indolent cutaneous ulcers. Early recognition of the problem and drug withdrawal can prevent complications like disfigurement.

Aplastic anemia secondary to azathioprine in systemic lupus erythematosus: report of a case with normal thiopurine S-methyltransferase enzyme activity and review of the literature

Azathioprine-induced aplastic anemia and fatal myelosuppression is a rare occurrence in patients with systemic lupus erythematosus (SLE). We report a case of a 53-year-old female with a normal thiopurine S-methyltransferase (TPMT) level who developed aplastic anemia within 4 weeks of azathioprine initiation, resulting in death. Physicians should be vigilant in monitoring routine blood work when administering azathioprine, a relatively common drug, in patients with SLE.

Pharmacogenetics: implications for therapy in rheumatic diseases

DMARDs not only improve the joint pain and swelling associated with rheumatoid arthritis (RA), but also slow down the joint damage associated with the disease. The efficacy of biologic therapies, introduced in the past decade for the treatment of RA, has been unequivocally established. Similarly, in addition to traditional drugs such as hydroxychloroquine, new biologic agents such as rituximab have been introduced for systemic lupus erythematosus in recent years. However, considerable variability occurs in the responses of patients to these therapies. Pharmacogenetics, the study of variations in genes encoding drug transporters, drug-metabolizing enzymes and drug targets, and their translation to differential responses to drugs, is a rapidly progressing field in rheumatology. Pharmacogenetic applications, particularly to the old vanguard DMARD, methotrexate, and the newer, more expensive biologic agents, might make personalized therapy in rheumatic diseases possible. The pharmacogenetics of commonly used DMARDs and of biologic therapies are described in this Review.

[Azathioprine-associated severe myelosuppression: indication of routine determination of thiopurine S-methyltransferase variant?]

INTRODUCTION

Myelotoxicity is a well-known adverse effect of azathioprine, leading mainly to leukopenia. Other azathioprine associated hematological adverse effects are uncommon.

CASE REPORT

We report a 49-year-old woman with rheumatoid arthritis and acquired hemophilia, who presented a severe myelosuppression occurring 3 weeks after an increase of her azathioprine regimen (at a daily dose of 150 mg). The patient had a heterozygous mutation of the thiopurine S-methyltransferase gene (TPMT*3A). Azathioprine therapy was discontinued and she recovered at 3 weeks. The patient had no relapse of pancytopenia after a 1 year follow-up.

CONCLUSION

Routine measurement of TPMT activity or determination of TPMT variant allele may be useful tests, in order to identify the subgroup of patients who are at risk to develop azathioprine induced severe myelosuppression.

Improving pharmacovigilance in Europe: TPMT genotyping and phenotyping in the UK and Spain

Thiopurine S-methyltransferase (TPMT) is the rate-limiting step in the conversion of thiopurine drugs including azathioprine (AZA) to inactive metabolites. Heritable deficiency of TPMT activity increases risk for adverse events, most notably, myelosuppression leading to leukopenia and neutropenic sepsis. The reported European Commission study was undertaken to identify current evidence for the clinical utility of testing for TPMT status and extent of uptake, by either genotyping or phenotyping, in the clinical setting. Data presented here for the UK and Spain indicate that there has been a considerable increase in the uptake of TPMT testing in recent years. There are some data that support routine TPMT testing before AZA prescribing for reducing AZA-related adverse events. Key data include evidence in favor of TPMT testing in addition to the current practice of routine monitoring for reducing the number of AZA-related episodes of myelosuppression, averting deaths from neutropenic sepsis and improving health-related quality of life. Further data are needed for determining the cost-effectiveness of routine TPMT testing.

TPMT testing in azathioprine: a ‘cost-effective use of healthcare resources’?

This study aimed to critically appraise the current level of economic evidence available for thiopurine S-methyltransferase (TPMT) testing of thiopurine drugs, such as azathioprine. Six economic evaluations of testing were identified, which all recommended that TPMT testing is a cost-effective use of healthcare resources. Critical appraisal, using published guidelines, showed potential limitations in model structures, approaches to data analysis and input parameters, which were mainly based on expert opinion. Where data did exist these were from retrospective studies. To conduct economic evaluations with more robust findings, decision analysts need good quality data for the following key parameters: current prevalence of profound neutropenia among patients prescribed thiopurine drugs; mean length of related hospitalization and clinical outcome; impact of introducing the test on clinical pathways in terms of resource use; and clinical effectiveness data in terms of number of cases of neutropenia averted and subsequent impact on mortality and health-related quality of life. An iterative approach may be used to stimulate the production of a sufficient evidence base for innovative technologies, such as pharmacogenetic testing. Such an iterative approach involves starting with simple models using available existing clinical and resource use data, as in the case of TPMT testing. The use of formal value of information methods may guide the decision whether prospective studies are required to address uncertainties in the key parameters driving the model results. The results from well-designed prospective studies can then be used to populate more complex economic models.