Polymorphism in IgA nephropathy

Epidemiologic data of renal diseases from a single unit in China: analysis based on 13,519 renal biopsies

Renal biopsy specimens of 13,519 cases were collected during the period of January 1979 to December 2002 from the Research Institute of Nephrology, Nanjing University School of Medicine, Nanjing, China. Analysis of the data of this group of patients showed that primary glomerulonephritis (GN) remained the most important and prevalent renal disease in China. The ratio of primary to secondary GN was 2.75:1. However, it is declining progressively in the past two decades with an increment in the incidence of diabetic nephropathy and nephrosclerosis. IgA nephropathy (IgAN) constituted 45.26% of the primary GN, while non-IgA mesangial proliferative lesions were 25.62%. Membranous nephropathy was 9.89% and minimal change disease was 0.93%, remarkably less. The most prevalent etiology of secondary GN was systemic lupus erythrematosus (SLE) (54.3%) followed by Henoch-Schönlein purpura (20.3%), diabetic nephropathy (6.6%), systemic vasculitides (4.0%), and amyloidosis (2.2%). Based on the study of biopsy materials obtained from 607 cases manifesting chronic renal failure, IgAN was identified as the most frequent cause (26.69%) of chronic renal failure.

ACE gene polymorphism and IgA nephropathy: an ethnically homogeneous study and a meta-analysis

BACKGROUND

Conflicting results have implicated the angiotensin-converting enzyme (ACE) D allele in the progression of renal damage in patients with IgA nephropathy (IgAN). Most of these findings have been obtained by heterogeneous studies.

METHODS

We investigated the ACE insertion/deletion (I/D) gene polymorphism by polymerase chain reaction (PCR) amplification of genomic DNA in an ethnically homogeneous sample size of IgAN patients from Southern Italy. The association between ACE I/D gene polymorphism and the development of the disease was examined in 247 biopsy-proven IgAN patients and 205 healthy subjects. The association with the progression of renal damage was evaluated in 136 patients with a follow-up of > or =3 years according to the slope of the creatinine clearance against time, and in 221 patients with a follow-up of > or =1 year assessing by univariate and multivariate analyses of renal survival. These associations were further estimated in a meta-analysis of seven studies retrieved in the Medline database. The meta-analysis was performed according to the Mantel-Haenszel-Peto method when homogeneity of the studies was established using the chi(2) test by Breslow-Day.

RESULTS

No difference in the ACE I/D gene distribution between patients and controls and between patients with stable and those with deteriorating renal function was found in our study. A meta-analysis performed separately for Caucasian and Asian studies showed that the ACE I/D gene polymorphism did not contribute to the genetic susceptibility of the development of IgAN (total OR 0.93, 95% CI, 0.71 to 1.23; and 0.95, 95% CI, 0.64 to 1.42, respectively) or the progression of the renal damage (total OR 1.12, 95% CI, 0.67 to 1.88; and 2.26, 95% CI, 0.75 to 6.79, respectively) in both groups.

CONCLUSIONS

Our study and meta-analysis suggest caution in the interpretation of results from association studies enrolling heterogeneous populations. Further studies using new tests, which are free of the bias due to population stratification and ethnicity, are warranted.

Mannose-binding lectin gene polymorphism associated with the patterns of glomerular immune deposition in IgA nephropathy

OBJECTIVE

To elucidate the genetic background underlying the diversity of mesangial immune deposition in IgA nephropathy (IgAN), we investigated the distribution of mannose-binding lectin (MBL) gene codon 54 polymorphism and serum MBL levels in IgAN patients.

METHODS

Seventy-seven IgAN patients with glomerular IgA and C3 deposits (Group A) and 70 with glomerular IgA, IgG, IgM, C3 and Clq deposits (Group AGM) were included in the present study. Control group consisted of 140 normal adults. MBL genotypes were investigated by polymerase chain reaction and restriction fragment length polymorphism. Serum MBL levels with different genotypes were also assayed in some subjects.

RESULTS

The variant allele (GAC) was markedly associated with Group AGM (OR = 1.95, 95% C.I.: 1.06-3.58). In both Group A and Group AGM, more patients carrying the variant allele had episodes of upper respiratory or gastrointestinal infections prior to onset or exacerbation of IgAN than wild homozygotes (GGC/GGC). In addition, a significant difference in serum MBL level was also observed between wild homozygotes and heterozygotes (GGC/GAC) (GGC/GGC > GGC/GAC) (p<0.0001) in all groups, while there was no difference for subjects with the same genotypes among the three groups (p > 0.05). Serum MBL levels of the rare variant homozygotes approached zero.

CONCLUSIONS

Our findings provide evidence that the host defense molecule, MBL, may be involved in the formation of the diversity of glomerular immune deposition in IgAN. Genetic deficiency of MBL may partially account for abundant immune deposits in some IgAN patients.