Propylthiouracil-induced antineutrophil cytoplasmic antibody (ANCA)-associated renal vasculitis versus primary ANCA-associated renal vasculitis: a comparative study

Thyroid disease in ANCA-associated vasculitis: a clinical and epidemiological study

OBJECTIVES

To describe clinical and laboratory characteristics and outcomes in patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and thyroid disease (TD). We also aimed to calculate incidence and identify predictors of TD in two large cohorts of patients with AAV.

METHODS

The study comprised 644 patients with AAV in a population-based cohort from southern Sweden (n=325) and a cohort from a specialised vasculitis centre in Cambridge, UK (n=319). Diagnosis and classification of AAV and TD were confirmed by medical record review. Person-years (PY) of follow-up were calculated from AAV diagnosis to the earliest of TD, death or the end of study. Cox-regression analysis was employed to study predictors of TD.

RESULTS

At AAV diagnosis, 100 individuals (15.5%, 77 females) had TD, 59 had myeloperoxidase (MPO)-ANCA+ and 34 had proteinase-3 (PR3)-ANCA+. Patients with TD tended to have lower C reactive protein, lower haemoglobin and fewer constitutional symptoms. Survival and renal survival was greater in those patients with AAV with pre-existing TD. During 4522 PY of follow-up, a further 29 subjects developed TD, yielding an incidence rate of 641/100 000 PY. No analysed factor predicted de novo TD in AAV. The prevalence of TD among patients with AAV in southern Sweden was 18%.

CONCLUSION

TD is a common comorbidity in AAV, affecting nearly one in five. While TD diagnosis is more common in females and MPO-ANCA+, these factors do not predict de novo TD after initiation of AAV treatment, necessitating monitoring of all patients with AAV with respect to this comorbidity.

Characteristics and outcome of ANCA-associated vasculitides induced by anti-thyroid drugs: a multicentre retrospective case-control study

OBJECTIVE

Data on ANCA-associated vasculitis (AAV) induced by anti-thyroid drugs (ATD) are scarce. We aimed to describe the characteristics and outcome of these patients in comparison to primary AAV.

METHODS

We performed a retrospective multicentre study including patients with ATD-induced AAV. We focused on ATD-induced microscopic polyangiitis (MPA) and compared them with primary MPA by matching each case with four controls by gender and year of diagnosis.

RESULTS

Forty-five patients with ATD-induced AAV of whom 24 MPA were included. ANCA were positive in 44 patients (98%), including myeloperoxidase (MPO)-ANCA in 21 (47%), proteinase 3 (PR3)-ANCA in six (13%), and double positive MPO- and PR3-ANCA in 15 (33%). Main clinical manifestations were skin involvement (64%), arthralgia (51%) and glomerulonephritis (20%). ATD was discontinued in 98% of cases, allowing vasculitis remission in seven (16%). All the remaining patients achieved remission after glucocorticoids, in combination with rituximab in 11 (30%) or cyclophosphamide in four (11%). ATD were reintroduced in seven cases (16%) without any subsequent relapse. Compared with 96 matched primary MPA, ATD-induced MPA were younger at diagnosis (48 vs 65 years, P < 0.001), had more frequent cutaneous involvement (54 vs 25%, P = 0.007), but less frequent kidney (38 vs 73%, P = 0.02), and a lower risk of relapse (adjusted HR 0.07; 95% CI 0.01, 0.65, P = 0.019).

CONCLUSION

ATD-induced AAV were mainly MPA with MPO-ANCA, but double MPO- and PR3-ANCA positivity was frequent. The most common manifestations were skin and musculoskeletal manifestations. ATD-induced MPA were less severe and showed a lower risk of relapse than primary MPA.

Animal models for anti-neutrophil cytoplasmic antibody-associated vasculitis: Are current models good enough?

Antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV) is a rare and severe systemic autoimmune disease characterized by pauci-immune necrotizing inflammation of small blood vessels. AAV involves multiple organ systems throughout the body. Our knowledge of the pathogenesis of AAV has increased considerably in recent years, involving cellular, molecular and genetic factors. Because of the controlled environment with no other confounding factors, animal models are beneficial for studying the mechanistic details of disease development and for providing novel therapeutic targets with fewer toxic side effects. However, the complexity and heterogeneity of AAV make it very difficult to establish a single animal model that can fully represent the entire clinical spectrum found in patients. The aim of this review is to overview the current status of animal models for AAV, outline the pros and cons of methods, and propose potential directions for future research.

A Spotlight on Drug-Induced Vasculitis

PURPOSE OF REVIEW

Drug-induced vasculitis (DIV) is a rare form of vasculitis related to the use of various drugs. DIV primarily affects small to medium size vessels, but it can potentially involve vessels of any size. Differentiating between primary systemic vasculitis and DIV can be challenging; however, it is crucial, so that the offending agent can be discontinued promptly.

RECENT FINDINGS

The clinical phenotype of DIV is protean and depends on the size of the affected vessels. It ranges from arthralgias, to an isolated cutaneous rash, to severe single or multi-organ involvement. While withdrawal of the offending drug is the most important step in management, a significant number of patients require immunosuppressive therapy for varying periods of time. DIV can affect any vascular bed size, leading to protean vasculitic syndromes. Increased awareness among general practitioners, specialty, and subspecialty physicians is crucial for early recognition, and withdrawal of drug for better outcomes.

A worldwide pharmacoepidemiological update of drug-associated ANCA-associated vasculitis at the time of targeted therapies

OBJECTIVE

The literature data supporting the role of a drug in the onset of drug-associated anti-neutrophil cytoplasmic antibody-associated vasculitis (DA-AAV) mainly rely on case reports or short series and implicate old treatments. The advent of new treatments may have modified the epidemiology of these adverse drug reactions (ADRs). We therefore aimed to update this list by using a pharmacovigilance-based data mining approach.

METHODS

We collected data on ADRs reported with the MedDRA preferred term "Anti-neutrophil cytoplasmic antibody positive vasculitis" up to November 2020 from the World Health Organization pharmacovigilance database (VigiBase^® ). For each retrieved drug, a case/noncase analysis was performed, and disproportionate reporting was calculated by using the information component (IC). A positive IC₀₂₅ value, which is the lower end of the 95% credibility interval, was considered significant.

RESULTS

A total of 483 deduplicated individual case safety reports of DA-AAV involving 15 drugs with an IC₀₂₅ >0 were retrieved. DA-AAV occurred in 264 (71.2%, n=371) women, the median age at onset was 62 years [45-72], and the median time to onset between the introduction of the suspected drug and DA-AAV was 9 months [1-36]. DA-AAV occurrence was considered serious in 472 (97.7%, n=481) cases and fatal in 43 (8.9%) cases. The drugs associated with the highest disproportionate reporting were hydralazine, propylthiouracil, thiamazole, sofosbuvir, minocycline, carbimazole, mirabegron, and nintedanib.

CONCLUSION

This study strengthens the previously suspected association but also identifies 3 new drugs that may cause DA-AAV. Particular attention should be given to these drugs by prescribers and in experimental studies.

Propylthiouracil-Induced Anti-Neutrophil Cytoplasmic Antibody Vasculitis Presenting with Red Eye Followed by Pulmonary Hemorrhage: Diagnostic and Management Considerations

Patient: Female, 34-year-old

Final Diagnosis: Vascuitis

Symptoms: Hemoptysis

Medication:—

Clinical Procedure: —

Specialty: Rheumatology

Comorbidities and health-related quality of life in Patients with Antineutrophil Cytoplasmic Antibody (ANCA) - associated vasculitis

BACKGROUND AND OBJECTIVES

The optimization of immunosuppressive therapies has led to a marked improvement in the survival of ANCA-associated vasculitides (AAV). The main issue now appears to be the management of comorbidities and the improvement of quality of life. The objective of this review was to investigate the incidence and the impact of AAV-associated comorbidities, as well as the determinants of health-related quality of life (HRQoL).

METHODS

We performed a systematic literature review of articles published in Medline from 2001 to 04/28/2020. We selected relevant articles about AAV-associated comorbidities as well as HRQoL and fatigue. For each selected article, data on the incidence of comorbidity were extracted, and factors associated with the Mental component score (MCS) and the Physical component score (PCS) were identified.

RESULTS

Among the 10,993 references identified, 103 were retained for the final analysis. A significant increase in cardiovascular risk was evidenced, particularly for coronary artery disease and thromboembolic events, especially during the active phase of the disease. AAV was also associated with bronchiectasis, thyroid diseases and osteoporosis. A marked decrease in HRQoL and an increase in fatigue and anxiety were reported. Decrease in PCS and MCS was associated with fatigue, mood disorders, sleep disturbance, and/or unemployment.

CONCLUSION

The excess mortality of AAV is still a concern, partly in connection with cardiovascular and thromboembolic comorbidities. AAV patients also experiment a reduction in their HRQoL that requires integrated management. Patients with AAV need comorbidity management strategies to improve their quality of life and outcomes.

Doxycycline-Induced Antinuclear Antibody and Antineutrophil Cytoplasmic Antibody Associated Vasculitis: A Case Report and Literature Review

Drug-induced antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) has been increasingly recognized in the literature with numerous medications listed as causative agents in disease pathology. Doxycycline is a commonly prescribed medication within the United States which is a synthetic, broad-spectrum antibiotic with antimicrobial properties and at low doses exhibits anti-inflammatory effects. In this report, we describe a case of doxycycline-induced ANCA-associated vasculitis with laboratory and biopsy findings supporting the diagnosis, which to the best of our knowledge is the first described case of doxycycline-induced AAV in the literature. The patient was started on doxycycline for treatment of potential Lyme disease. She began to develop progressively worsening myasthenia, erythematous macular rash, anorexia, anemia, and fatigue for several weeks following the course of doxycycline with initial concern of a paraneoplastic process. Ultimately, the patient was discovered to be positive for antinuclear antibody (ANA), perinuclear antineutrophil cytoplasmic antibody (pANCA), and myeloperoxidase (MPO) antibody for which she was treated with a course of prednisone leading to complete remission of disease. A brief review of the pathogenesis of ANCA vasculitides will also be discussed within this article.

Drug-induced anti-neutrophil cytoplasmic antibody-associated vasculitis

OBJECTIVE

In recent years, an increasing number of drugs have been proved to be associated with the induction of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). This article reviews the latest research progress on drug-induced AAV.

DATA SOURCES

We conducted a comprehensive and detailed search of the PubMed database. The search terms mainly included drug-induced, ANCA, and vasculitis.

STUDY SELECTION

We summarized the original articles and reviews on drug-induced AAV in recent years. The extracted information included the definition, epidemiology, associated drugs, pathogenesis, clinical features, diagnosis, treatment, and prognosis of drug-induced AAV. We also focused on the differences between drug-induced AAV and primary vasculitis.

RESULTS

The offending drugs leading to drug-induced AAV are almost from pharmacologic categories and we need to be vigilant when using these drugs. The pathogenesis of drug-induced AAV might be multifactorial. The formation of neutrophil extracellular traps is an important mechanism for the development of drug-induced AAV. The clinical features of drug-induced AAV are similar to those of primary AAV. Understanding the difference between drug-induced AAV and primary AAV is helpful to identify drug-induced AAV. Stopping the offending drug at once after diagnosis may be sufficient for those patients with mild symptoms. Immunosuppressive therapy should only be used in patients with vital organs involvement.

CONCLUSIONS

Patients with drug-induced AAV usually have a good prognosis if they stop using the offending drug immediately. Recent advances in research on AAV are expected to help us better understand the pathogenesis of drug-induced AAV.

Antineutrophil cytoplasmic antibodies-associated glomerulonephritis: From bench to bedside

Antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) is a group of autoimmune disorders that predominantly affects small vessels. The onset of the disease is closely associated with ANCA. Renal involvement, also known as ANCA-associated glomerulonephritis (AGN), is one of the most common manifestations of AAV. In this mini-review, we described the clinical and pathological features of AGN. We then focused on recent studies on the mechanism of acute kidney lesions, including fibrinoid necrosis and crescent formation. Following the basic aspects of kidney injury in AGN, we demonstrated the clinical importance of kidney injury in determining the outcome of patients with AGN. The prognostic value of the 2010 Histopathological Classification of AGN and validating studies were summarized. Finally, treatment and novel therapeutic strategies were introduced addressing the importance of optimizing management of this patient population.

Clinical Characteristics and Outcomes of Propylthiouracil-Induced Antineutrophil Cytoplasmic Antibody-Associated Vasculitis in Patients with Graves' Disease: A Median 38-Month Retrospective Cohort Study from a Single Institution in China

BACKGROUND

This study sought to investigate the clinical characteristics and outcomes of propylthiouracil (PTU)-induced antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis in patients with Graves' disease.

METHODS

Sixteen patients diagnosed with PTU-induced ANCA-associated vasculitis at the authors' hospital from January 2010 to June 2017 were analyzed retrospectively.

RESULTS

All 16 patients with PTU-induced ANCA-associated vasculitis were female. The mean age ± standard deviation of the patients was 39.4 ± 15.3 years (range 19-69 years), and the median time of onset was 36 months (range 1-193 months) post-PTU initiation. The median dose at the onset of PTU-induced ANCA-associated vasculitis was 150 mg/day (range 50-300 mg/day). All patients had a positive serum perinuclear staining pattern (p-ANCA) and antibodies directed against myeloperoxidase (anti-MPO). Six patients tested positive for both anti-MPO antibodies and antibodies directed against proteinase-3. Seven (43.8%) patients presented with involvement of a single organ. The kidney was the organ most commonly affected, as 12 (75%) patients were found to have disease involving this organ. PTU was stopped in all patients, corticosteroids were administered to two patients, and immunosuppressive agents and corticosteroids were administered to five patients. Three patients were lost to follow-up. However, the remaining patients achieved remission after a median follow-up period of 38 months (range 6-76 months). Patients who were positive for pANCA and displayed cytoplasmic staining showed negative findings at rates of approximately 53.8% (7/13) and 100% (6/6), respectively, following treatment.

CONCLUSIONS

PTU-induced ANCA-positive vasculitis occurs at varying times and after exposure to various doses of PTU. The condition has a milder course and has a better prognosis after PTU cessation.

Guidelines for the treatment of childhood-onset Graves' disease in Japan, 2016

Purpose behind developing these guidelines: Over one decade ago, the “Guidelines for the Treatment of Graves’ Disease with Antithyroid Drug, 2006” (Japan Thyroid Association (JTA)) were published as the standard drug therapy protocol for Graves’ disease. The “Guidelines for the Treatment of Childhood-Onset Graves’ Disease with Antithyroid Drug in Japan, 2008” were published to provide guidance on the treatment of pediatric patients. Based on new evidence, a revised version of the “Guidelines for the Treatment of Graves’ Disease with Antithyroid Drug, 2006” (JTA) was published in 2011, combined with the “Handbook of Radioiodine Therapy for Graves’ Disease 2007” (JTA). Subsequently, newer findings on pediatric Graves’ disease have been reported. Propylthiouracil (PTU)-induced serious hepatopathy is an important problem in pediatric patients. The American Thyroid Association’s guidelines suggest that, in principle, physicians must not administer PTU to children. On the other hand, the “Guidelines for the Treatment of Graves’ Disease with Antithyroid Drug, 2011” (JTA) state that radioiodine therapy is no longer considered a “fundamental contraindication” in children. Therefore, the “Guidelines for the Treatment of Childhood-Onset Graves’ Disease with Antithyroid Drug in Japan, 2008” required revision.

Histopathological Classification and Renal Outcome in Patients with Antineutrophil Cytoplasmic Antibodies-associated Renal Vasculitis: A Study of 186 Patients and Metaanalysis

Objective.

Renal vasculitis is one of the most common manifestations of antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) and renal histology is a key predictor of the outcome. A new histopathologic classification was proposed and validated, but the results are still debated.

Methods.

We performed a retrospective analysis to validate the histopathologic classification and performed a metaanalysis to evaluate its predictive value. There were 186 patients with ANCA-associated renal vasculitis diagnosed at Ruijin Hospital who were enrolled in the retrospective study. The metaanalysis considered the data for 1601 patients.

Results.

In our retrospective study, patients with focal class had the best renal outcome while patients with mixed class had the worst (p < 0.001). Metaanalysis showed that patients with focal class had better renal outcome than did those with crescentic class [risk ratio (RR) 0.23, 95% CI 0.16–0.34, p < 0.00001], with no evidence of heterogeneity (I2 = 0%, p = 0.96). Patients with crescentic class had better renal outcome than did those with sclerotic class (RR 0.52, 95% CI 0.41–0.64, p < 0.00001), with no evidence of heterogeneity (I2 = 2%, p = 0.43). We did not find statistical significance regarding renal outcome between mixed and crescentic classes (RR 1.14, 95% CI 0.91–1.43, p = 0.27), with no evidence of heterogeneity (I2 = 23%, p = 0.19). The retrospective study showed that lung and upper respiratory tract involvement were the most common extrarenal manifestations.

Conclusion.

We demonstrated the clinical utility of histopathologic classification in determining renal outcome in patients with AAV. Metaanalysis showed that patients with focal class had the best outcome while sclerotic class had the worst.

Antineutrophil Cytoplasmic Antibody-Positive Small-Vessel Vasculitis Associated with Antithyroid Drug Therapy: How Significant Is the Clinical Problem?

BACKGROUND

The aim of this review was to delineate the characteristics of antineutrophil cytoplasmic antibody (ANCA)-associated small-vessel vasculitis associated with antithyroid drugs (ATD). A PubMed search was made for English language articles using the search terms antithyroid drugs AND ANCA OR ANCA-associated vasculitis.

SUMMARY

The literature includes approximately 260 case reports of ANCA-associated small-vessel vasculitis related to ATD, with 75% of these associated with thiouracil derivatives (propylthiouracil [PTU]) and 25% with methyl-mercapto-imidazole derivatives (MMI/TMZ). The prevalence of ANCA-positive cases caused by ATD varied between 4% and 64% with PTU (median 30%), and 0% and 16% with MMI/TMZ (median 6%). Young age and the duration of ATD therapy were the main factors contributing to the emergence of ANCA positivity. Before ATD therapy initiation, the prevalence of ANCA-positive patients was 0-13%. During ATD administration, 20% of patients were found to be positive for ANCA. Only 15% of ANCA-positive patients treated with ATD exhibited clinical evidence of vasculitis, corresponding to 3% of all patients who received ATD. Clinical manifestations of ANCA-associated vasculitis related to ATD were extremely heterogeneous. When vasculitis occurred, ATD withdrawal was usually followed by rapid clinical improvement and a favorable prognosis.

CONCLUSIONS

ANCA screening is not systematically recommended for individuals on ATD therapy, particularly given the decreasing use of PTU in favor of TMZ/MMI. Particular attention should be given to the pediatric population with Graves' disease who receive ATD, as well as patients treated with thiouracil derivatives and those on long-term ATD therapy.

Drug-induced glomerular disease: immune-mediated injury

Drug-induced autoimmune disease was initially described decades ago, with reports of vasculitis and a lupus-like syndrome in patients taking hydralazine, procainamide, and sulfadiazine. Over the years, multiple other agents have been linked to immune-mediated glomerular disease, often with associated autoantibody formation. Certain clinical and laboratory features may distinguish these entities from their idiopathic counterparts, and making this distinction is important in the diagnosis and management of these patients. Here, drug-induced, ANCA-associated vasculitis, drug-induced lupus, and drug-associated membranous nephropathy are reviewed.

Trojan horses: drug culprits associated with antineutrophil cytoplasmic autoantibody (ANCA) vasculitis

PURPOSE OF REVIEW

Antineutrophil cytoplasmic autoantibody (ANCA) vasculitis is a systemic autoimmune disease resulting in small-vessel inflammation caused by pathogenic autoantibodies directed against proteinase 3 or myeloperoxidase. Legal drug culprits have been implicated as causative agents in secondary forms of disease, and a recent burst of reports also implicate levamisole-adulterated cocaine as a culprit.

RECENT FINDINGS

Here, we briefly discuss all drug culprits associated with ANCA vasculitis and then focus on clinical, serologic, therapeutic and mechanistic aspects of four main drug culprits receiving attention of late, namely hydralazine, minocycline, propylthiouracil (PTU) and levamisole-adulterated cocaine.

SUMMARY

Hydralazine, minocycline, propylthiouracil and levamisole-adulterated cocaine use should be closely considered in any patient where ANCA vasculitis is entertained given the wide use of these drugs in the community. Furthermore, medical practitioners should test urine for the presence of cocaine in any patient with presumed ANCA vasculitis, and if positive, then urine should also be tested for levamisole. Clinical features can be severe requiring not only drug cessation and supportive care, but also immunosuppression, plasma exchange in severe cases and dialysis as needed. Clinical trial investigators should strongly consider excluding patients with drug-induced forms of disease and mechanistic inroads are greatly needed in these secondary forms of disease to help elucidate the underlying cause and pathogenesis of ANCA vasculitis.

Clinico-pathological features and outcomes of patients with propylthiouracil-associated ANCA vasculitis with renal involvement

OBJECTIVE

To retrospectively investigate clinico-pathological features and outcomes of patients with renal involvement in propylthiouracil (PTU)-associated antineutrophil cytoplasmic autoantibody (ANCA) vasculitis (PTU-AAV).

METHODS

Clinico-pathological features and outcomes of 12 patients (female 11, average age 32.4 ± 13.8 years) who developed AAV after treatment with PTU were collected and analyzed. ANCA was detected by both immunofluorescence (IF) and enzyme linked immunosorbent assay (ELISA). All patients had renal biopsy.

RESULTS

Twelve patients received PTU for 2-264 months (median 42 months) when PTUAAV was diagnosed. All patients had positive serum P-ANCA, 11 of them were MPO-ANCA, 1 was MPO and PR3-ANCA double positive. All patients presented with hematuria and proteinuria, 5 of them had gross hematuria, urine protein was 1.9 ± 1.6 g/24 h, 7 of 12 (58.3%) patients had renal dysfunction, among them 3 needed initial renal replacement therapy. Renal biopsy showed pauci-immune segmental necrotizing crescentic glomerulonephritis in ten patients, segmental necrotizing glomerulonephritis superimposed on membranous nephropathy in two patients. All patients withdrew PTU and received steroid and immunosuppressive therapy. After a median follow-up of 42 months (range 21-86), 3 patients developed to ESRD, 7 patients entered complete renal remission. Serum ANCA turned negative only in 2 patients, 10 patients had persistent positive serum ANCA. Three patients relapsed with the elevation of serum ANCA level.

CONCLUSION

Renal damage of PTU-AAV could be pauci-immune necrotizing crescentic glomerulonephritis, and necrotizing glomerulonephritis coexisted with membranous nephropathy. Most patients had persistent positive serum ANCA and had a risk of relapse and progression to ESRD even after PTU withdrawal and immunosuppressive therapy.

Acute febrile neutrophilic dermatosis (Sweet's syndrome)

PURPOSE OF REVIEW

To highlight the recent observations regarding not only research but also the clinical features and management of Sweet's syndrome.

RECENT FINDINGS

Some of the new insights concerning Sweet's syndrome include: (1) bortezomib-induced Sweet's syndrome (some of which are the histiocytoid variant), (2) a rare extracutaneous manifestation of Sweet's syndrome with cardiovascular involvement including coronary artery occlusion, and (3) the possibility that photosensitivity may have a role in the pathogenesis of Sweet's syndrome.

SUMMARY

Animal models of Sweet's syndrome and new associated medication have been observed. The definitive mechanism of pathogenesis still remains to be elucidated. Recent observations in paediatric patients suggest evaluation of dermatosis-related cardiac involvement in patients with post-Sweet's syndrome cutis laxa. Treatment advances include antitumour necrosis factor- alpha drugs; however, these medications have also been associated with inducing Sweet's syndrome. Nearly 50 years after the initial description of an acute febrile neutrophilic dermatosis by Dr Robert Douglas Sweet, the dermatosis remains a fascinating condition with regard to laboratory investigation, clinical manifestations and treatment.

Propylthiouracil-induced antineutrophil cytoplasmic antibody-associated vasculitis

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) refers to a group of potentially life-threatening autoimmune diseases. A recent development in this field is the recognition that certain drugs can induce AAV. Among these agents, the drug most often implicated in causing disease is the commonly used antithyroid agent propylthiouracil (PTU). This Review provides an update on PTU-induced AAV. Clinical characteristics of PTU-induced AAV are similar to that of primary AAV, but usually have a milder course and better prognosis, provided early cessation of the disease-causing drug. PTU-induced ANCAs usually react to several components of myeloid granules, which is helpful in differentiating PTU-induced AAV from primary AAV. Early cessation of PTU is crucial in the treatment of PTU-induced AAV. The duration of immunosuppressive therapy might be shorter than in primary AAV, depending on the severity of organ damage, and maintenance therapy is not always necessary.