Rheumatology International

, Volume 30, Issue 10, pp 1311–1315

Male gender results in more severe lupus nephritis

Authors

    • Rheumatology Division, Faculdade de MedicinaUniversidade de São Paulo e Hospital das Clínicas
  • Ana Patrícia do Nascimento
    • Rheumatology Division, Faculdade de MedicinaUniversidade de São Paulo e Hospital das Clínicas
  • Leonardo A. Testagrossa
    • Pathology Department, Faculdade de MedicinaUniversidade de São Paulo e Hospital das Clínicas
  • Rui Toledo Barros
    • Nephrology Divisions, Faculdade de MedicinaUniversidade de São Paulo e Hospital das Clínicas
  • Eloísa Bonfá
    • Rheumatology Division, Faculdade de MedicinaUniversidade de São Paulo e Hospital das Clínicas
Original Article

DOI: 10.1007/s00296-009-1151-9

Cite this article as:
de Carvalho, J.F., do Nascimento, A.P., Testagrossa, L.A. et al. Rheumatol Int (2010) 30: 1311. doi:10.1007/s00296-009-1151-9

Abstract

Gender may produce different characteristics in the manifestation of systemic lupus erythematosus (SLE). The present study investigated the influence of gender on clinical, laboratory, autoantibodies and histopathological classes of lupus nephritis (LN). As much as 81 patients diagnosed with SLE (ACR criteria) and active nephritis, who underwent renal biopsy between 1999 and 2004, and who had frozen serum samples and clinical data available from the time of biopsy, were selected for this study. The presence of anti-P and antichromatin antibodies was measured using ELISA, and anti-dsDNA was measured using indirect immunofluorescence. All of the renal biopsies were reviewed in a blinded manner by the same expert renal pathologist. The charts were extensively reviewed for demographic and renal features obtained at the time of the biopsy. Of the 81 patients (13.6%), 11 were male SLE patients. Both male and female lupus patients were of similar age and race, and had similar durations of lupus and renal disease. The female patients had more cutaneous (95.7 vs. 45.5%, P = 0.0001) and haematological (52.9 vs. 18.2%, P = 0.04) involvements than the male SLE patients. In addition, the articular data, central nervous system analyses, serositis findings and SLEDAI scores were similar in both experimental groups. Positivity for anti-dsDNA, anti-ribosomal P and antichromatin did not differ between the two groups, and both groups showed similarly low C3 or C4 serum levels. Our analysis indicated that no histopathological class of LN was predominant in both males and females. Interestingly, the serum creatinine levels were higher in the male SLE patients compared to the female SLE group (3.16 ± 2.49 vs. 1.99 ± 1.54 mg/dL, P = 0.03), with an increased frequency of high creatinine (81.8 vs. 47.1%, P = 0.04) as well as renal activity index (7.6 ± 3.5 vs. 4.8 ± 3.5, P = 0.02). In addition, whilst the mean levels of proteinuria, cylindruria and serum albumin were markedly altered, they were comparable between both lupus men and women. Moreover, the frequencies of dialysis, renal transplantation and death were similar between the two groups. These data suggest that male patients had a more severe LN compared to women diagnosed with this renal abnormality.

Keywords

Systemic lupus erythematosusLupus nephritisGenderPrognosisAutoantibodiesKidney involvement

Introduction

Systemic lupus erythematosus (SLE) is a relapsing chronic multisystemic disease characterised by periods of disease activity followed by remission that predominantly affects women of childbearing age. Indeed, the majority of rheumatic autoimmune diseases have a greater incidence in females [1].

Several studies have demonstrated that male SLE patients present atypical manifestations of this disease, typically have a significantly worse prognosis and have a more serious kidney involvement [2, 3]. However, another report did not find any significant differences in lupus clinical complications observed between female and male patients [4].

More specifically, with regard to lupus renal prognoses, a very recent study has addressed the sex-based differences in Indian lupus patients and demonstrated that renal dysfunction and the renal activity index were worse in male patients compared to female patients [5]. However, this study did not address other parameters such as autoantibodies, complement levels or parameters regarding prognosis involving the dialysis frequency, renal transplantation or mortality.

Therefore, the study presented herein investigated the influence of gender on: clinical data, laboratory analyses, histopathological classes, autoantibodies, renal prognostics and severity data in lupus glomerulonephritis patients with biopsy-proven LN using a large sample size.

Patients and methods

Patients

As much as 81 patients with biopsy-proven systemic LN diagnosed between 1999 and 2004 were selected based on the availability of frozen serum samples obtained at the time of the renal biopsy. All of the patients fulfilled the revised ACR criteria for SLE [6]. In addition, all of the biopsy specimens were reviewed by the same expert renal pathologist (LAT) in a blinded manner, and the resulting histological findings were recorded according to the 2004 criteria established by the International Society of Nephrology and the Renal Pathology Society for the classification of lupus glomerulonephritis [7]. The local ethics committee approved the protocol for this study, and informed consent was obtained from all participants.

Clinical evaluation

Individual medical charts belonging to the selected patients were retrospectively reviewed for demographic, clinical and renal features at the time of biopsy by one of the authors (APN), who was blinded to the antibody profile data.

Renal involvement

Evidence for active renal SLE at the time of biopsy, using parameters from the SLEDAI score [8], was based on persistent proteinuria (≥0.5 g/24 h), the presence of cellular casts and evidence of haematuria (≥10 red blood cells (RBC)/hpf and/or ≥5/hpf leukocytes, excluding cases of infection and nephrolithiasis). The serum creatinine level at a concentration of ≥1.5 mg/dL was arbitrarily defined as an indicator of renal dysfunction.

Detection of autoantibodies

The serum sample obtained from each patient at the time of biopsy was initially screened at a 1:40 dilution for the presence of antinuclear antibodies by indirect immunofluorescence (IIF) on HEp-2 cells. The anti-dsDNA antibody was detected using IIF on Crithidia luciliae as described previously [9]. The antichromatin antibodies were assayed using ELISA as described previously. These assays were performed with a commercially available kit employing highly purified H1-stripped chromatin [DNA wrapped around the core of the histone octamer (H2A-H2B-H3-H4)2, Quanta Lite™ Chromatin, Inova Diagnostics, San Diego, CA, USA] from calf thymus as source of antigens, following the manufacturer’s protocol. The antibody level was reported according to the manufacturer’s optical density units, and values that were ≥20 U were defined as positive. The serum samples were tested in duplicate using two different batches of the kit to ensure the reproducibility of the results [10]. Anti-ribosomal P (anti-P) antibodies were detected with ELISA as described previously [11] using high-binding polystyrene microtitre plates (Corning Costar, Corning, NY, USA) sensitised with recombinant human P2 polypeptide (kindly provided by Dr. K. B. Elkon, University of Washington, Seattle, WA, USA) and were blocked with 1% bovine serum albumin in a solution of phosphate-buffered saline (PBS) for 1 h. The serum samples were then diluted 1:100 in PBS containing 0.1% Tween 20, 10% normal goat serum and 10% wild Escherichia coli total extract to prevent nonspecific binding. In this assay, any results that were higher than the mean value of 40 normal sera plus 3 SD were considered positive. The specificity of the anti-P antibody ELISA was confirmed in all sera by performing Western blot assays using the purified ribosomal fraction isolated from rat hepatocytes as a substrate [12].

Measurement of the C3/C4 complement components

The serum levels of C3 and C4 complement components were determined using the immunodiffusion test (Dade Behring Marburg, Marburg, Germany). The normal range for C3 was 84–167 mg/dL, whilst the normal range for C4 was 16–31 m/dL.

Statistical analysis

The data are presented as the mean ± SD or as a percentage. Fisher’s exact test, Chi-square test and t test were applied to analyse the associations between variables using the GraphPad Instat V 2.0 software. In addition, P values less than 0.05 were considered to be of statistical significance.

Results

Amongst the 81 patients with biopsy-proven active LN, 11 (13.6%) were male and 70 were (86.4%) female. Overall, the male and female SLE patients had the following similar: mean age (35.1 ± 11.9 years vs. 32.1 ± 9.5 years, P = 0.35), frequency of members from the black race (45.5 vs. 44.3%, P = 1.00), SLEDAI scores (9.0  ±  4.0 vs. 8.4 ± 3.6, P = 0.28), duration of lupus (5.0 ± 4.3 vs. 6.5 ± 4.8 years, P = 0.34) and duration of renal disease (3.8 ± 2.9 years vs. 4.8 ± 3.7 years, P = 0.39, Table 1).
Table 1

The demographics, clinical data and SLEDAI scores of the 81 male and female patients diagnosed with lupus nephritis (LN)

 

LN males (n = 11)

LN females (n = 70)

P

Mean age

35.1 ± 11.9

32.1 ± 9.5

0.35

Black race n (%)

5 (45.5)

31 (44.3)

1.00

Disease duration (years)

5.0 ± 4.3

6.5 ± 4.8

0.34

Renal disease duration (years)

3.8 ± 2.9

4.8 ± 3.7

0.39

Cutaneous n (%)

5 (45.5)

67 (95.7)

0.0001

Articular n (%)

10 (90.9)

69 (98.6)

0.25

Haematological n (%)

2 (18.2)

37 (52.9)

0.04

Central nervous system n (%)

4 (36.4)

19 (27.1)

0.50

Serositis n (%)

5 (45.5)

14 (20)

0.12

SLEDAI score

8.5 ± 3.7

8.6 ± 3.8

0.89

Data are expressed as the mean ± SD or as a percentage

A lower frequency of cutaneous (45.5 vs. 95.7%, P = 0.0001) and haematological involvements (18.2 vs. 52.9%, P = 0.04) was observed in male lupus patients on comparison with the female patients. The prevalence of articular, serositis and central nervous system diseases was also comparable between the two groups (Table 1).

Autoantibody positivity values were similar in both male and female patients regarding the presence of anti-dsDNA, anti-ribosomal P and antichromatin. Likewise, the frequency of low serum levels for C3 (72.7 vs. 48.6%, P = 0.19) and C4 (63.6 vs. 57.1%, P = 0.75), as well as the mean levels for C3 (60.4 ± 42.9 vs. 283.4 ± 163 mg/dL, P = 0.67) and C4 (8.2 ± 11.8 vs. 13.8 ± 14.4 mg/dL, P = 0.24), were comparable between the two groups of patients (Table 2).
Table 2

The autoantibody positivity and complement levels of the 81 male and female patients diagnosed with lupus nephritis (LN)

 

LN males (n = 11)

LN females (n = 70)

P

Anti-dsDNA n (%)

7 (63.6)

27 (38.6)

0.19

Anti-P n (%)

2 (18.2)

16 (22.9)

1.00

Antichromatin n (%)

7 (63.6)

25 (35.7)

0.11

C3 (mg/dL)

60.4 ± 42.9

283.4 ± 163

0.67

Low C3

8 (72.7)

34 (48.6)

0.19

C4 (mg/dL)

8.2 ± 11.8

13.8 ± 14.4

0.24

Low C4 (%)

7 (63.6)

40 (57.1)

0.75

Data are expressed as the mean ± SD or as a percentage

Analysis of the histopathological class distribution of LN revealed no predominance of any class of lupus nephritis in either male or female lupus patients. Moreover, higher creatinine serum levels were observed in patients from the male lupus group (3.16 ± 2.49 vs. 1.99 ± 1.54 mg/dL, P = 0.03) as well as an increased frequency of high creatinine (81.8 vs. 47.1%, P = 0.04) in comparison to the female group. Similarly, the frequency of haematuria was significantly higher in male patients than in female patients (81.8 vs. 77.1%, P < 0.0001). There was no significant difference observed between male and female patients regarding the level of proteinuria (4.2 ± 2.2 vs. 5.2 ± 4.4 g/24 h, P = 0.45), the level of cylindruria (72.7 vs. 65.7, P = 0.74) and the serum albumin levels (2.3 ± 0.7 vs. 2.6 ± 0.8 g/L, P = 0.25, Table 3).
Table 3

The histopathology, renal parameters and deaths of the 81 male and female patients diagnosed with lupus nephritis (LN)

 

LN males (n = 11)

LN females (n = 70)

P

LN class II n (%)

0

3 (4.3)

1.00

LN class III n (%)

2 (18.2)

7 (10)

0.60

LN class IV n (%)

4 (36.4)

30 (42.9)

0.75

LN class V n (%)

5 (45.5)

30 (42.9)

1.00

SLEDAI score

8.5 ± 3.7

8.6 ± 3.8

0.89

Proteinuria (g/24 h)

4.2 ± 2.2

5.2 ± 4.4

0.45

Serum creatinine (mg/dL)

3.16 ± 2.49

1.99 ± 1.54

0.03

Creatinine ≥1.5 mg/dL n (%)

9 (81.8)

33 (47.1)

0.04

Albumin (g/dL)

2.3 ± 0.7

2.6 ± 0.8

0.25

Haematuriaa (RBC/hpf)

62.5 ± 42.4

58.6 ± 43.9

0.78

Haematuria n (%)

9 (81.8)

54 (77.1)

<0.0001

Cylindruria n (%)

8 (72.7)

46 (65.7)

0.74

Activity index

7.6 ± 3.5

4.8 ± 3.5

0.02

Chronicity index

4.5 ± 3.5

2.8 ± 2.8

0.10

Dialysis n (%)

3 (27.3)

12 (17.1)

0.42

Renal transplantation n (%)

1 (9)

2 (2.8)

0.36

Deaths n (%)

2 (18.2)

5 (7.1)

0.24

Data are expressed as the mean ± SD or as a percentage

aHaematuria ≥10 red blood cells (RBC)/hpf

In addition, the renal activity index in patients from the male group was statistically higher (7.6 ± 3.5 vs. 4.8 ± 3.5, P = 0.02) than that observed in patients from the female group. However, the renal chronicity index (4.5 ± 3.5 vs. 2.8 ± 2.8, P = 0.10) was similar between the two groups. The frequencies of dialysis (27.3 vs. 17.1%, P = 0.42), renal transplantation (9 vs. 2.8%, P = 0.36) and deaths (18.2 vs. 7.1%, P = 0.24) were also similar in the male and female SLE patient groups (Table 3).

Discussion

The results of the study presented herein suggest that males have more severe lupus nephritis, as indicated by higher creatinine levels and by comparison of the histopathological activity index values when compared to female patients with this renal condition.

Glomerulonephritis is a major determinant of the prognosis of SLE. The underlying pathogenic mechanisms of glomerulonephritis may involve the in situ formation or the deposition of circulating immune complexes in the renal tissue in addition to the direct cytotoxicity of a subset of pathogenic autoantibodies that are cross-reactive to intrinsic glomerular cell antigens [13, 14]. Several autoantibodies have emerged as potential biomarkers for the diagnosis of lupus renal disease with promising results, such as anti-dsDNA, anti-actinin, anti-P, anti-C1q and anti-L [1517]. In fact, patients with these antibodies had a higher prevalence of LN when compared to those individuals without these antibodies [13, 18]. The findings presented herein confirm the presence of these antibodies in a large sample size of patients diagnosed with biopsy-proven active LN, although no sex-based associations were observed.

Several authors have demonstrated a more aggressive lupus disease in males characterised by a higher rate of complications, mainly including lupus kidney involvement [1922]. Moreover, various studies have shown that renal dysfunction in male SLE patients was the major cause of SLE-related morbidity and mortality [19, 20, 23]. Our data provide evidence for a correlation between the male gender and a more severe form of lupus glomerulonephritis, which was possible by the inclusion of a significant number of patients who were diagnosed with biopsy-proven LN, in addition to the availability of serum samples obtained at the time of their clinical procedure.

Previous studies have identified some predictors of treatment resistance and relapse that include increasing serum creatinine levels and higher histological activity scores [24]. All of these factors were more commonly observed in the male SLE patients. Furthermore, the activity index score for the first biopsy correlated directly with the percentage of glomerulosclerosis, whilst the serum creatinine level obtained at the second biopsy suggested that this parameter was a very important indicator of the overall prognosis and may predict its evolution [25].

In conclusion, male patients with lupus nephritis appear to have a greater severity of renal impairment as indicated by higher creatinine and activity renal index values in comparison with SLE women.

Acknowledgments

Dr. Bonfa’s work was supported by grant 305468/2006-5 from the Conselho Nacional de Desenvolvimento Científico e Tecnológico–CNPq and by the Federico Foundation grant. Dr. Carvalho′s work was supported by the Federico Foundation grant.

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© Springer-Verlag 2009