Anti-neutrophil cytoplasmic antibody associated glomerulonephritis complicating treatment with hydralazine
Authors: Dominick Santoriello, Andrew S. Bomback, Satoru Kudose, Ibrahim Batal, M. Barry Stokes, Pietro A. Canetta, Jai Radhakrishnan, Gerald B. Appel, Vivette D. D’Agati, Glen S. Markowitz
Journal: Kidney International (2021)

Hydralazine, a widely used therapy for hypertension and heart failure, can elicit autoimmune disease, including anti-neutrophil cytoplasmic antibody associated glomerulonephritis (ANCA-GN). We identified 80 cases of ANCA-GN complicating treatment with hydralazine, accounting for 4.3% (80/1858 biopsies) of ANCA-GN diagnosed between 2006 and 2019. Over three-fourths of patients were on hydralazine for at least one year, with mean daily dose of approximately 250 mg/day. ANCA testing revealed p-ANCA/myeloperoxidase-ANCA seropositivity in 98%, including 39% with dual p-ANCA/myeloperoxidase-ANCA and cANCA/anti-protinase 3-ANCA positivity, often accompanied by anti-nuclear antibody (89%), anti-histone antibody (98%), and hypocomplementemia (58%). Kidney biopsy revealed necrotizing and crescentic glomerulonephritis, similar to primary ANCA-GN, but significantly less frequently pauci-immune (77 vs. 100%) and more commonly associated with mesangial hypercellularity (30 vs. 5%), electron dense deposits (62 vs. 20%), and endothelial tubuloreticular inclusions (11 vs. 0%); all significant differences. On follow-up, 42 of 51 patients received induction immunosuppression: 19 reached the combined end-points of kidney failure or death and 32 had mean creatinine of 1.49 mg/dL at last follow-up. Thus, hydralazine-associated ANCA-GN often exhibits overlapping clinical and pathologic features of mild immune complex glomerulonephritis resembling lupus nephritis. With discontinuation of hydralazine and immunosuppression, outcomes are similar to primary ANCA-GN. Hydralazine, a widely used therapy for hypertension and heart failure, can elicit autoimmune disease, including anti-neutrophil cytoplasmic antibody associated glomerulonephritis (ANCA-GN). We identified 80 cases of ANCA-GN complicating treatment with hydralazine, accounting for 4.3% (80/1858 biopsies) of ANCA-GN diagnosed between 2006 and 2019. Over three-fourths of patients were on hydralazine for at least one year, with mean daily dose of approximately 250 mg/day. ANCA testing revealed p-ANCA/myeloperoxidase-ANCA seropositivity in 98%, including 39% with dual p-ANCA/myeloperoxidase-ANCA and cANCA/anti-protinase 3-ANCA positivity, often accompanied by anti-nuclear antibody (89%), anti-histone antibody (98%), and hypocomplementemia (58%). Kidney biopsy revealed necrotizing and crescentic glomerulonephritis, similar to primary ANCA-GN, but significantly less frequently pauci-immune (77 vs. 100%) and more commonly associated with mesangial hypercellularity (30 vs. 5%), electron dense deposits (62 vs. 20%), and endothelial tubuloreticular inclusions (11 vs. 0%); all significant differences. On follow-up, 42 of 51 patients received induction immunosuppression: 19 reached the combined end-points of kidney failure or death and 32 had mean creatinine of 1.49 mg/dL at last follow-up. Thus, hydralazine-associated ANCA-GN often exhibits overlapping clinical and pathologic features of mild immune complex glomerulonephritis resembling lupus nephritis. With discontinuation of hydralazine and immunosuppression, outcomes are similar to primary ANCA-GN. Treatment with or exposure to certain drugs can elicit the generation of autoantibodies and clinical autoimmune disease affecting the kidneys, including immune complex–mediated or pauci-immune glomerulonephritis (GN) and membranous glomerulopathy.1Hogan J.J. Markowitz G.S. Radhakrishnan J. Drug-induced glomerular disease: immune-mediated injury.Clin J Am Soc Nephrol. 2015; 10: 1300-1310Crossref PubMed Scopus (46) Google Scholar Clinical awareness of drug-induced autoimmune disease is important given the need to discontinue the offending agent in the management of these conditions. Drugs associated with anti–neutrophil cytoplasmic antibody (ANCA)–associated vasculitis (AAV) include propylthiouracil, cocaine adulterated with levamisole, tumor necrosis factor-α inhibitors, and hydralazine.1Hogan J.J. Markowitz G.S. Radhakrishnan J. Drug-induced glomerular disease: immune-mediated injury.Clin J Am Soc Nephrol. 2015; 10: 1300-1310Crossref PubMed Scopus (46) Google Scholar, 2Stokes M.B. Foster K. Markowitz G.S. et al.Development of glomerulonephritis during anti-TNF-alpha therapy for rheumatoid arthritis.Nephrol Dial Transplant. 2005; 20: 1400-1406Crossref PubMed Scopus (187) Google Scholar, 3Pendergraft W.F. Niles J.L. Trojan horses: drug culprits associated with antineutrophil cytoplasmic autoantibody (ANCA) vasculitis.Curr Opin Rheumatol. 2014; 26: 42-49Crossref PubMed Scopus (88) Google ScholarEditor's NoteThis study is perhaps the largest and most detailed investigation of the clinical and kidney histopathologic features of anti–neutrophil cytoplasmic antibody–associated vasculitis (AAV) occurring in the setting of hydralazine use. Hydralazine has also been associated with lupus-like syndromes, and several of the patients described here seemed to have features of both AAV and lupus. Hydralazine affects DNA methylation and B-cell tolerance, and fosters NETosis, all of which could contribute to induction of autoimmunity in susceptible patients. Given the array of effective, and possibly less toxic, anti-hypertensive medications available today, the Editorial Board wondered whether hydralazine was used very much anymore. An informal poll among nephrology colleagues showed considerable variation in use worldwide. In Canada, the Unites States, and Australia, it is used frequently, and often by cardiologists when renin-angiotensin system blockers are contraindicated. It is rarely used in Mexico, Argentina, mainland China, Hong Kong, Singapore, and Japan. In India, hydralazine is used mainly by cardiologists for congestive heart failure in patients with chronic kidney disease. It is not used in France, the Czech Republic, or Germany, and only rarely in the Netherlands, United Kingdom, and Russia. We suspect that cases of hydralazine-associated AAV will continue to be found, maybe more so in patients with cardiovascular disease, and it will be important for nephrologists to keep this in mind as we consult for our cardiology colleagues. This study is perhaps the largest and most detailed investigation of the clinical and kidney histopathologic features of anti–neutrophil cytoplasmic antibody–associated vasculitis (AAV) occurring in the setting of hydralazine use. Hydralazine has also been associated with lupus-like syndromes, and several of the patients described here seemed to have features of both AAV and lupus. Hydralazine affects DNA methylation and B-cell tolerance, and fosters NETosis, all of which could contribute to induction of autoimmunity in susceptible patients. Given the array of effective, and possibly less toxic, anti-hypertensive medications available today, the Editorial Board wondered whether hydralazine was used very much anymore. An informal poll among nephrology colleagues showed considerable variation in use worldwide. In Canada, the Unites States, and Australia, it is used frequently, and often by cardiologists when renin-angiotensin system blockers are contraindicated. It is rarely used in Mexico, Argentina, mainland China, Hong Kong, Singapore, and Japan. In India, hydralazine is used mainly by cardiologists for congestive heart failure in patients with chronic kidney disease. It is not used in France, the Czech Republic, or Germany, and only rarely in the Netherlands, United Kingdom, and Russia. We suspect that cases of hydralazine-associated AAV will continue to be found, maybe more so in patients with cardiovascular disease, and it will be important for nephrologists to keep this in mind as we consult for our cardiology colleagues. Hydralazine, an arterial vasodilator, is widely used as an anti-hypertensive agent and in the management of heart failure. Drug-induced autoimmunity, including drug-induced AAV and drug-induced lupus, is a long-recognized potential complication of hydralazine use. Drug-induced lupus occurs in 5% to 10% of patients receiving hydralazine, and is characterized by the development of anti-nuclear autoantibodies (ANAs) and anti-histone antibodies and symptoms that include myalgias, fever, and serositis.4Hess E. Drug-related lupus.N Engl J Med. 1988; 318: 1460-1462Crossref PubMed Scopus (171) Google Scholar Renal involvement is uncommon.5Yokogawa N. Vivino F.B. Hydralazine-induced autoimmune disease: comparison to idiopathic lupus and ANCA-positive vasculitis.Mod Rheumatol. 2009; 19: 338-347Crossref PubMed Google Scholar AAV appears to be a rare complication, with <100 cases reported to date.6Kumar B. Strouse J. Swee M. et al.Hydralazine-associated vasculitis: overlapping features of drug-induced lupus and vasculitis.Semin Arthritis Rheum. 2018; 48: 283-287Crossref PubMed Scopus (16) Google Scholar However, the true incidence of AAV is unknown. In one series, 10 of 30 patients with AAV and the highest titers of anti-myeloperoxidase (MPO) antibodies had been exposed to hydralazine.7Choi H.K. Merkel P.A. Walker A.M. Niles J.L. Drug-associated antineutrophil cytoplasmic antibody-positive vasculitis: prevalence among patients with high titers of antimyeloperoxidase antibodies.Arthritis Rheum. 2000; 43: 405-413Crossref PubMed Scopus (282) Google Scholar Hydralazine-induced lupus and AAV may show considerable overlap.6Kumar B. Strouse J. Swee M. et al.Hydralazine-associated vasculitis: overlapping features of drug-induced lupus and vasculitis.Semin Arthritis Rheum. 2018; 48: 283-287Crossref PubMed Scopus (16) Google Scholar The clinical course of hydralazine-associated AAV is dominated by rapidly progressive GN. Extrarenal disease, including pulmonary involvement, is rare. In addition to high-titer MPO-ANCA, serologic evaluation typically reveals positive ANA and anti-histone autoantibodies and hypocomplementemia.7Choi H.K. Merkel P.A. Walker A.M. Niles J.L. Drug-associated antineutrophil cytoplasmic antibody-positive vasculitis: prevalence among patients with high titers of antimyeloperoxidase antibodies.Arthritis Rheum. 2000; 43: 405-413Crossref PubMed Scopus (282) Google Scholar Descriptions of biopsy-proven hydralazine-associated ANCA-GN are largely limited to case reports and small case series, most of which reveal pauci-immune necrotizing and crescentic GN.5Yokogawa N. Vivino F.B. Hydralazine-induced autoimmune disease: comparison to idiopathic lupus and ANCA-positive vasculitis.Mod Rheumatol. 2009; 19: 338-347Crossref PubMed Google Scholar However, systematic and detailed descriptions of histologic, immunofluorescence (IF), and ultrastructural findings, as well as comparisons to primary ANCA-GN and reports on long-term follow-up, are lacking. Herein, we report 80 patients diagnosed with ANCA-GN while on hydralazine, the largest kidney biopsy series to date, providing detailed descriptions of clinical-pathologic findings and long-term follow-up. We also compare key clinical and pathologic features with a control group of primary ANCA-GN. All native kidney biopsies with a diagnosis of ANCA-associated GN accessioned at the Columbia University Renal Pathology Laboratory from 2006 to 2019 were reviewed for a history of treatment with hydralazine preceding renal biopsy. Inclusion criteria included: (i) predominant light microscopic findings of necrotizing and crescentic GN; (ii) ANCA seropositivity; and (iii) a history of treatment with hydralazine. Exclusion criteria included a known history of AAV, systemic lupus erythematosus, or other autoimmune/connective tissue disease before treatment with hydralazine, commencement of treatment with hydralazine only at the time of initial presentation with acute kidney injury, and known exposure to other drugs associated with AAV (including propylthiouracil, cocaine, or anti–tumor necrosis factor-α therapy). Seventy-five consecutive biopsies from 2016 showing primary ANCA-GN, in the absence of a documented history of treatment with hydralazine, were utilized as a comparison group of select initial clinical and demographic features as well as pathologic findings. Biopsies from patients with documented exposure to hydralazine, propylthiouracil, cocaine, or anti–tumor necrosis factor-α therapy were excluded from the comparison group, as were biopsies with overlapping serologic or IF evidence of anti–glomerular basement membrane nephritis. All kidney biopsies were processed according to standard techniques for light microscopy, IF, and electron microscopy and were interpreted by 1 of 6 renal pathologists. For IF, 3-μm frozen sections were stained with fluorescein isothiocyanate–conjugated rabbit anti-human IgG, IgM, IgA, C3, C1q, and κ and λ light chain (Dako). The submitting nephrologists provided the following information: patient demographics, medical history, systemic findings of extrarenal AAV, duration of hydralazine use, daily dose of hydralazine at time of kidney biopsy, requirement for renal replacement therapy at presentation, serum creatinine at presentation, urine protein-to-creatinine ratio or 24-hour urine protein level, presence of hematuria (>5 cells/high-power field), anti-nuclear antibody, anti-histone antibodies, double-stranded DNA antibodies, serum complements, anti-neutrophil cytoplasmic antibodies, lupus anticoagulant, and anti-cardiolipin antibodies. In addition, follow-up information regarding serum creatinine, repeated serologic testing, and type of treatment was obtained. The following pathologic parameters were collected: (i) predominant light microscopic pattern of glomerular injury; (ii) number of total and globally sclerotic glomeruli; (iii) percentage of glomeruli with cellular or fibrocellular crescents; (iv) percentage glomeruli with fibrous crescents; (v) percentage of cortex with interstitial fibrosis and tubular atrophy; (vi) degree of interstitial inflammation (scale, 0–3; none indicates 0; mild (0%–25%), 1; moderate (26%–50%). 2; or severe (>50%), 3); (vii) degree of vascular sclerosis (scale, 0–3); (viii) presence of coexisting disease process; (ix) intensity of IF staining (scale, 0–3+); (x) presence and location of electron-dense deposits; and (xi) presence or absence of endothelial tubuloreticular inclusions. Histopathologic classifications were assigned according to the scheme described by Berden et al.8Berden A.E. Ferrario F. Hagen E.C. et al.Histopathologic classification of ANCA-associated glomerulonephritis.J Am Soc Nephrol. 2010; 21: 1628-1636Crossref PubMed Scopus (463) Google Scholar Pauci-immune was defined as staining of ≤1+ intensity for all immune reactants, on an intensity scale graded from 0 to 3+. Baseline characteristics for patients were presented descriptively, with mean ± SD for continuous variables and percentage for categorical variables. We compared initial clinical and biopsy parameters between patients with hydralazine-associated ANCA GN and a comparison group with primary ANCA-associated GN using a 2-sample Wilcoxon rank-sum (Mann-Whitney) test for continuous variables and the Fisher exact test for categorical variables. Analyses were performed using STATA version 12.1 (StataCorp). This study was approved by the Institutional Review Board of Columbia University Irving Medical Center. We identified 80 patients who developed kidney biopsy-proven ANCA-GN, all of whom were taking hydralazine before presentation, accounting for 4.3% (80/1858 biopsies) of all ANCA-GN diagnosed between 2006 and 2019 in our practice. Clinical data at the time of biopsy are provided in Table 1. The mean age was 69 years, and 61% of patients were female. The cohort self-identified as 69% White, 16% Black, and 6% Latinx. Duration of hydralazine use before kidney biopsy was available for 47 patients (59%) in whom the length of time was <12 months in 11 (23%; minimal duration, 5 months), 12 to 60 months in 29 (62%), and >60 months in 7 (15%). Daily doses of hydralazine at the time of kidney biopsy were available from 30 patients, with mean 254 ± 88 mg/d.Table 1Clinical data at biopsy of 80 patients with hydralazine-associated glomerulonephritisDemographic and clinical parametersResultsDemographics Age, yr69.3 ± 10.7 Female sex49 (61.3) Race/ethnicityWhite55 (68.8)Black13 (16.3)Latino5 (6.3)Asian0 (0)Other1 (1.3)Unknown6 (7.5)Laboratory data and serologies Serum creatinine, mg/dl4.3 ± 2.6 Urinary protein, g/d or g/g2.6 ± 3.1 Hematuria80 (100) ANA (n = 74)66 (89.2) dsDNA Ab (n = 49)22 (44.9) Anti-histone Ab (n = 46)45 (97.8) Hypocomplementemia (n = 66)38 (57.6) ANCAp-ANCA or MPO Ab only47 (58.8)c-ANCA or PR3 Ab only2 (2.5)Dual ANCA (+)31 (38.8)Duration of hydralazine therapy, mo (N = 47) <1211 (23.4) 12–6029 (61.7) >607 (14.9)Ab, antibody; ANA, anti-nuclear antibody; ANCA, anti–neutrophil cytoplasmic antibody; c-, cytoplasmic; dsDNA, double-stranded DNA; MPO, myeloperoxidase; p-, perinuclear; PR3, proteinase 3.Data are given as mean ± SD or n (%). Open table in a new tab Ab, antibody; ANA, anti-nuclear antibody; ANCA, anti–neutrophil cytoplasmic antibody; c-, cytoplasmic; dsDNA, double-stranded DNA; MPO, myeloperoxidase; p-, perinuclear; PR3, proteinase 3. Data are given as mean ± SD or n (%). Mean serum creatinine at the time of biopsy was 4.3 mg/dl. Thirteen patients (16%) were dialysis dependent at presentation. Mean proteinuria was 2.6 g/d or g/g by 24-hour collection or spot urine protein-to-creatinine ratio. ANA and double-stranded DNA antibody were detected in 89% (66 of 74) and 45% (22 of 49) of tested patients, respectively. Anti-histone antibody was detected in nearly all patients tested (45 of 46 [98%]). Hypocomplementemia was present in 58% (38 of 66) of patients, including 28 with depressed C3 and C4, 8 with depressed C3 only, and 2 with depressed C4 only. Lupus anticoagulant and anti-cardiolipin antibodies were detected in 5 of 10 (50%) and 11 of 16 (69%) patients, respectively. All patients were ANCA positive. Specifically, 47 patients (59%) were positive for p-ANCA and/or MPO antibody only, 31 (39%) were dual ANCA positive, and 2 (2.5%) were positive for c-ANCA and/or proteinase 3 (PR3) antibody only. All patients had negative testing for anti–glomerular basement membrane antibody. At the time of kidney biopsy, 14 patients (18%) had documented clinical and/or radiologic evidence of pulmonary involvement (including 5 with hemoptysis), 3 (3.8%) had purpuric skin rash, and 2 (2.5%) had clinical evidence of upper airway tract involvement by vasculitis. In all 80 biopsies (Table 28Berden A.E. Ferrario F. Hagen E.C. et al.Histopathologic classification of ANCA-associated glomerulonephritis.J Am Soc Nephrol. 2010; 21: 1628-1636Crossref PubMed Scopus (463) Google Scholar), the dominant light microscopic pattern of injury was necrotizing and crescentic GN (Figure 1a), with mean percentage global sclerosis of 24%, mean percentage of glomeruli with cellular/fibrocellular crescents of 23%, and mean percentage of glomeruli with fibrous crescents of 4.5%. The mean percentage of "intact glomeruli" (devoid of crescents) was 48%. According to the classification by Berden et al.,8Berden A.E. Ferrario F. Hagen E.C. et al.Histopathologic classification of ANCA-associated glomerulonephritis.J Am Soc Nephrol. 2010; 21: 1628-1636Crossref PubMed Scopus (463) Google Scholar 6.3% were sclerotic class, 51.3% were focal class, 11.3% were crescentic class, and 31.3% were mixed class (Table 28Berden A.E. Ferrario F. Hagen E.C. et al.Histopathologic classification of ANCA-associated glomerulonephritis.J Am Soc Nephrol. 2010; 21: 1628-1636Crossref PubMed Scopus (463) Google Scholar). The mean percentage of glomeruli with fibrinoid necrosis was 16.5%, generally involving glomeruli with cellular or fibrocellular crescents. Mesangial hypercellularity was documented in 24 biopsies (30%) (Figure 1b). Obliterative endocapillary proliferation (7.5%) and membranous features (2.5%) were rare. The degree of interstitial fibrosis and tubular atrophy was mild (0%–25%) in 33 biopsies (41%), moderate (26%–50%) in 36 biopsies (45%), and severe (>50%) in 11 biopsies (14%). The overall mean degree of interstitial fibrosis and tubular atrophy was 32%, mean interstitial inflammation was 1.6 (graded 0–3), and mean arteriosclerosis was 1.9 (graded 0–3). Necrotizing arteritis was seen in only 3 biopsies (3.8%). Findings of necrotizing and crescentic GN were superimposed on background changes of diabetic glomerulosclerosis in 15 biopsies (19%).Table 2Pathology data of 80 subjects with hydralazine-associated glomerulonephritisPathologic parametersResultsLight microscopy Globally sclerotic, %24.3 ± 16.0 Normal glomeruli, %47.8 ± 22.3 Glomeruli with cellular or fibrocellular crescents, %23.3 ± 20.5 Glomeruli with fibrous crescents, %4.5 ± 8.7 Necrotizing arteritis3 (3.8) Interstitial inflammation (score, 0–3)1.6 ± 0.8 Mesangial hypercellularity24 (30) Endocapillary proliferation6 (7.5) Membranous2 (2.5) IFTA, %32.1 ± 19.4 Arteriosclerosis (score, 0–3)1.9 ± 0.9 Underlying NDGS15 (18.8)ImmunofluorescencePauci-immune62 (77.5) Positive immunofluorescence18 (22.5)IgG, no. positive (mean intensity)16 (1.9)IgM, no. positive (mean intensity)16 (1.6)IgA, no. positive (mean intensity)4 (1.8)C3, no. positive (mean intensity)18 (1.7)C1, no. positive (mean intensity)5 (1.4) Full house0 (0) Extraglomerular deposits5 (6.3)Electron microscopy (n = 74) % With immune deposits46 (62.2)Mesangial45 (60.8)Subendothelial21 (28.4)Subepithelial13 (17.6) % TRIs8 (10.8) ANCA classification8Berden A.E. Ferrario F. Hagen E.C. et al.Histopathologic classification of ANCA-associated glomerulonephritis.J Am Soc Nephrol. 2010; 21: 1628-1636Crossref PubMed Scopus (463) Google ScholarSclerotic5 (6.3)Focal41 (51.3)Crescentic9 (11.3)Mixed25 (31.3)ANCA, anti–neutrophil cytoplasmic antibody; IFTA, interstitial fibrosis and tubular atrophy; NDGS, nodular diabetic glomerulosclerosis; TRI, tubuloreticular inclusion.Data are given as mean ± SD or n (%), unless otherwise indicated. Open table in a new tab ANCA, anti–neutrophil cytoplasmic antibody; IFTA, interstitial fibrosis and tubular atrophy; NDGS, nodular diabetic glomerulosclerosis; TRI, tubuloreticular inclusion. Data are given as mean ± SD or n (%), unless otherwise indicated. By IF, 62 biopsies (78%) were classified as pauci-immune, 40 of which showed trace to 1+ intensity mesangial staining for at least one immune reactant, including IgG (65% [26 of 40]), IgM (83% [33 of 40]), IgA (20% [8 of 40]), C3 (70% [28 of 40]), or C1 (23% [9 of 40]). The remaining 18 biopsies showed >1+ intensity staining (scale, 0–3+) for at least one immune reactant, including IgG (16 of 18 [89%]; mean intensity, 1.9 ± 0.9), IgM (16 of 18 [89%]; mean intensity, 1.6 ± 0.7), IgA (4 of 18 [22%]; mean intensity, 1.8 ± 1.1), C3 (18 of 18 [100%]; mean intensity, 1.7 ± 0.7), or C1 (5 of 18 [28%]; mean intensity, 1.4 ± 0.6) (Figure 1c). Most were IgG dominant or codominant. None of the 80 biopsies showed full-house staining or linear glomerular basement membrane staining for IgG typical of anti–glomerular basement membrane nephritis. Five biopsies (6.3%) displayed granular immune-type staining for IgG and complement involving the tubulointerstitial and/or vascular compartments, none of which were classified as pauci-immune. Electron microscopy was performed in 74 biopsies, of which 46 (62%) had detectable electron-dense deposits. Mesangial deposits were most frequent (61% [45 of 74]) and ranged from segmental to global (Figure 1d). Subendothelial (28% [21 of 74]) and subepithelial (18% [13 of 74]) deposits were less common and were always segmental. Among the 62 pauci-immune biopsies, electron microscopy was performed in 55 and showed detectable immune deposits in 23 (42%). Endothelial tubuloreticular inclusions (i.e., "interferon footprints") were detected in 8 biopsies (11%). We compared clinical and pathologic features of hydralazine-associated ANCA-GN with 75 consecutive biopsies from a single year diagnosed as primary ANCA-GN. There were no significant differences in age and sex distribution (Table 3). Compared with primary ANCA-GN, patients with hydralazine-associated ANCA-GN had a significantly higher rate of ANA positivity (89% vs. 19%; P < 0.001) and hypocomplementemia (58% vs. 9.3%; P < 0.001), were more likely to be dual ANCA positive (39% vs. 3%; P < 0.001), and were less likely to be positive for only c-ANCA/PR3 antibody (2.5% vs. 29%; P < 0.001). Compared with primary ANCA-GN, hydralazine-associated ANCA-GN was more often focal class and less often sclerotic class, according to the Berden et al. classification system.8Berden A.E. Ferrario F. Hagen E.C. et al.Histopathologic classification of ANCA-associated glomerulonephritis.J Am Soc Nephrol. 2010; 21: 1628-1636Crossref PubMed Scopus (463) Google Scholar Mesangial hypercellularity was more common in patients on hydralazine (30% vs. 5.3%; P < 0.001). Endocapillary proliferation and membranous features were infrequent but also more common; however, this did not reach statistical significance (7.5% vs. 1.3% [P = 0.06] and 2.5% vs. 0% [P = 0.2], respectively). Biopsies from patients on hydralazine were less frequently pauci-immune by IF (78% vs. 100%; P < 0.001) and were more likely to have immune-type electron-dense deposits on electron microscopy (62% vs. 20%; P < 0.001). Tubuloreticular inclusions, although infrequent, were also more common in patients taking hydralazine (11% vs. 0%; P = 0.005). Among the patients with hydralazine-associated ANCA-GN, we compared the biopsy findings between patients with pauci-immune IF (n = 62) with those with IF positivity (n = 18). Non–pauci-immune IF biopsies had similar rates of ANA positivity (90% vs. 89%; P = 1.0), dual ANCA positivity (50% vs. 35%; P = 0.2), and hypocomplementemia (59% vs. 57%; P = 0.9) compared with biopsies that met criteria for pauci-immune. However, the non–pauci-immune cases demonstrated higher rates of mesangial hypercellularity (55% vs. 22%; P = 0.005) than the pauci-immune cases.Table 3Hydralazine GN versus ANCA-GNVariableHydralazine GN (n = 80)ANCA-GN (n = 75)P valueAge, yr69.3 ± 10.766.5 ± 16.10.2Female sex49 (61.3)46 (61.3)1.0Race/ethnicity<0.001 White55 (68.8)34 (45.3) Black13 (16.3)6 (8.0) Latino5 (6.3)8 (10.7) Asian0 (0)1 (1.3) Other1 (1.3)0 (0) Unknown6 (7.5)26 (34.7)Serum creatinine, mg/dl4.3 ± 2.64.2 ± 3.10.9ANA66 (89.2)14 (18.7)<0.001Hypocomplementemia38 (57.6)7 (9.3)<0.001ANCA<0.001 p-ANCA or MPO Ab47 (58.8)51 (68.0) c-ANCA or PR3 Ab2 (2.5)22 (29.3) Dual ANCA (+)31 (38.7)2 (2.7)Globally sclerotic, %24.3 ± 16.025.0 ± 22.40.9Normal glomeruli, %47.8 ± 22.340.2 ± 25.20.05Glomeruli with cellular or fibrocellular crescents, %23.3 ± 20.526.9 ± 21.10.3Glomeruli with fibrous crescents, %4.5 ± 8.78.2 ± 11.50.03Necrotizing arteritis3 (3.7)11 (14.7)0.02Interstitial inflammation (score, 0–3)1.6 ± 0.82.0 ± 0.90.01Mesangial hypercellularity24 (30)4 (5.3)<0.001Endocapillary proliferation6 (7.5)1 (1.3)0.06Membranous2 (2.5)0 (0)0.2IFTA, %32.1 ± 19.433.5 ± 25.40.7Arteriosclerosis (score, 0–3)1.9 ± 0.91.4 ± 0.90.003Pauci-immune IF62 (77.5)75 (100)<0.001Deposits by EM46 (62.2)15 (20)<0.001TRIs by EM8 (10.8)0 (0)0.005ANCA classification8Berden A.E. Ferrario F. Hagen E.C. et al.Histopathologic classification of ANCA-associated glomerulonephritis.J Am Soc Nephrol. 2010; 21: 1628-1636Crossref PubMed Scopus (463) Google Scholar<0.001 Sclerotic5 (6.3)11 (14.7) Focal41 (51.3)29 (38.7) Crescentic9 (11.3)12 (16.0) Mixed25 (31.3)23 (30.7)Ab, antibody; ANA, anti-nuclear antibody; ANCA, anti–neutrophil cytoplasmic antibody; c-, cytoplasmic; EM, electron microscopy; GN, glomerulonephritis; IF, immunofluorescence; IFTA, interstitial fibrosis and tubular atrophy; MPO, myeloperoxidase; p-, perinuclear; PR3, proteinase 3; TRI, tubuloreticular inclusion.Data are given as mean ± SD or n (%). Open table in a new tab Ab, antibody; ANA, anti-nuclear antibody; ANCA, anti–neutrophil cytoplasmic antibody; c-, cytoplasmic; EM, electron microscopy; GN, glomerulonephritis; IF, immunofluorescence; IFTA, interstitial fibrosis and tubular atrophy; MPO, myeloperoxidase; p-, perinuclear; PR3, proteinase 3; TRI, tubuloreticular inclusion. Data are given as mean ± SD or n (%). Follow-up data (Table 4) was available from 51 patients (64%), with median duration of 15.2 months. Hydralazine was discontinued in all patients. Forty-two received induction immunosuppressive therapy, including corticosteroids in 41 (80%), cyclophosphamide in 13 (26%), rituximab in 29 (57%), plasmapheresis in 9 (18%), and mycophenolate mofetil in 2 (3.9%). Specifically, among the 42 patients who received immunosuppression, 27 received rituximab, 11 received cyclophosphamide, 2 received both agents, and 2 received neither of the 2 agents. Eight patients (16%) received maintenance therapy, including azathioprine in 6 (12%) and mycophenolate mofetil in 2 (3.9%). During the period of follow-up, 14 patients (27%) progressed to end-stage kidney disease (ESKD), and 11 (21%) expired, including 6 who reached ESKD before death. Thus, 19 of 51 patients (37%) reached the combined end point of death or ESKD. Among the remaining 32 patients, the mean serum creatinine at end of follow-up was 1.49 (range, 1.18–1.97) mg/dl. On repeated testing, which followed discontinuation of treatment with hydralazine, 11 of 16 patients (69%) with available data had positive ANA and 2 of 9 patients (22%) had hypocomplementemia. Sixteen of 30 patients (53%) remained ANCA positive at time of last follow-up, with median (range) of follow-up of 237 (25–1144) days, including 14 with p-ANCA and/or MPO antibody positivity and 2 with dual ANCA positivity. Among 9 patients not receiving induction immunosuppression, 3 (33%) reached the combined end point of death or ESKD. The remaining patients had a median creatinine of 1.5 mg/dl (range, 1.3–5.0 mg/dl), all of which had biopsies classified as Berden class 2 (i.e., focal di