Major histocompatibility complex antigens in steroid-responsive nephrotic syndrome

Clinical and genetic heterogeneity in familial steroid-sensitive nephrotic syndrome

BACKGROUND

Familial steroid-sensitive nephrotic syndrome (SSNS) is a rare condition. The disease pathophysiology remains elusive. However, bi-allelic mutations in the EMP2 gene were identified, and specific variations in HLA-DQA1 were linked to a high risk of developing the disease.

METHODS

Clinical data were analyzed in 59 SSNS families. EMP2 gene was sequenced in families with a potential autosomal recessive (AR) inheritance. Exome sequencing was performed in a subset of 13 families with potential AR inheritance. Two variations in HLA-DQA1 were genotyped in the whole cohort.

RESULTS

Transmission was compatible with an AR (n = 33) or autosomal dominant (AD, n = 26) inheritance, assuming that familial SSNS is a monogenic trait. Clinical features did not differ between AR and AD groups. All patients, including primary (n = 7) and secondary steroid resistant nephrotic syndrone (SRNS), (n = 13) were sensitive to additional immunosuppressive therapy. Both HLA-DQA1 variations were found to be highly linked to the disease (OR = 4.34 and OR = 4.89; p < 0.001). Exome sequencing did not reveal any pathogenic mutation, neither did EMP2 sequencing.

CONCLUSIONS

Taken together, these results highlight the clinical and genetic heterogeneity in familial SSNS. Clinical findings sustain an immune origin in all patients, whatever the initial steroid-sensitivity. The absence of a variant shared by two families and the HLA-DQA1 variation enrichments suggest a complex mode of inheritance.

Two new families with hereditary minimal change disease

BACKGROUND

Steroid-sensitive idiopathic nephrotic syndrome (SSINS) is most often encountered in sporadic cases of minimal change disease (MCD). Only rare cases of familial forms of MCD have been reported and most of them only in one generation. The scarcity of data has precluded unraveling the underlying genetic defect and candidate gene approaches have been unsuccessful. Here we report two families with related SSINS cases and review the related literature.

CASE PRESENTATION

Two siblings and a cousin (first family), and a father and his son (second family), are reported with SSINS due to MCD. Patients have been followed up for more than 12 years and a renal biopsy was performed in three cases, demonstrating typical features of MCD. The course of the disease was remarkable because of several relapses treated with steroids. In three cases, mycophenolate mofetil or cyclosporine was added.

CONCLUSION

Familial SSINS due to MCD is extremely rare and no genetic defect has been identified so far. Reporting cases of hereditary MCD will allow further genetic studies which will ultimately help unravel the molecular basis of this disease.

HLA alleles in frequently relapsing steroid-dependent and -resistant nephrotic syndrome in Egyptian children

The association between HLA class II antigens and childhood primary nephrotic syndrome has been reported in different populations. To investigate this association in Egyptian children, DRB1 alleles were typed by DNA polymerase chain reverse hybridization in 20 frequent relapsers/steroid-dependent and 14 steroid-resistant children with minimal change nephrotic syndrome (MCNS) and 121 unrelated healthy controls from the northern part of Egypt. The strength of the association was expressed as the relative risk (RR) estimated by the odds ratio. The DRBI*07011 allele frequency was significantly higher among patients than controls (78.9% vs. 16%, Pc <0.001). The etiological fraction (EF) was high at 0.75 [RR=20.1, confidence interval (CI)=6.0-66.7]. Similarly, patients with steroid-resistant MCNS had a higher frequency of the DRBI*07011 allele than controls (64.3% vs. 16.5%, P c<0.001). The EF was high at 0.57 (RR=9.6, CI 2.9-31.7). In the whole group of patients the frequency of DRBI*11 alleles was low compared with controls (11.4% vs. 32.2%, P =0.02), but was not significant when P was corrected. In conclusion, the DRBI*07011 allele confers susceptibility to a frequently relapsing and steroid-dependent or steroid-resistant course of childhood MCNS. These patterns of the disease seem to have the same immunogenetic components.

Familial nephrotic syndrome: clinical spectrum and linkage to chromosome 19q13

BACKGROUND

Familial nephrotic syndrome (NS) has both autosomal dominant and recessive forms of inheritance. Recent studies in families with an autosomal dominant form of focal segmental glomerulosclerosis (FSGS) have been at odds concerning linkage to chromosome 19q13 (Mathis et al, Kidney Int 53:282-286, 1998; Winn et al, Kidney Int 55:1241-1246, 1999), suggesting genetic heterogeneity. This study examines the clinical features and confirms linkage to chromosome 19q13 in a family with autosomal dominant NS.

METHODS

DNA samples were obtained from 16 of 17 family members. Genomic DNA was isolated, and polymerase chain reaction was performed for five markers spanning the area of interest on chromosome 19q13. Data were evaluated using two- and six-point linkage analysis.

RESULTS

Clinical features included presentation of NS in childhood, steroid unresponsiveness, and slow progression to renal failure. Renal biopsy in affected family members showed lesions ranging from minimal change to mesangial proliferative glomerulonephritis to FSGS. Linkage was confirmed between the disease state and chromosome 19q13, with a maximum logarithm of odds (LOD) score of 2.41. Linkage was observed for a 7 cM region on chromosome 19q13, defined by markers D19S425 and D19S220.

CONCLUSIONS

This study confirms the Mathis et al report of linkage to chromosome 19q13 in a family with autosomal dominant NS. However, there were notable differences in the presenting clinical and histopathologic features of our affected family members compared with those of Mathis et al. This suggests that the gene on chromosome 19q13 may be responsible for considerable phenotypic heterogeneity and variable expression in both clinical presentation and renal histopathology.

Major histocompatibility complex antigens and immune mechanisms in steroid-responsive nephrotic syndrome

Although the pathogenesis of steroid-responsive nephrotic syndrome (SRNS) is obscure, involvement of an immune mechanism is often suggested. Further evidence of an immune basis for this disorder is an increased frequency of specific major histocompatibility complex (MHC) antigens. In the first part of this study, the phenotypic frequency of HLA-A, -B, -C, -DR antigens were investigated in 30 children with SRNS and in 630 controls. In the second part, total T (CD3+ cells) and B lymphocytes (CD19+ cells) and the lymphocyte subsets (CD4+, CD8+ cells and their ratio) were studied in the same patients and in 30 healthy children. The investigations of all patients were performed during the acute stage and 14 of 30 during remission stage. Human leukocyte antigens (HLA) were determined by standard microlymphocytotoxicity assay and lymphocytes were analyzed by flow cytometry. Human leukocyte antigens A3, DR4, DR7 and the haplotype HLA-A2/B12 showed the strongest association with SRNS. In the studies for cellular immune disorder, CD3+ and CD8+ cells were found to be decreased significantly in the acute stage before beginning steroid therapy. No significant difference in lymphocyte subsets was observed in the remission stage without steroid or immunosuppressive therapy.

HLA class II associations with idiopathic nephrotic syndrome in children

The occasional familial occurrence of idiopathic nephrotic syndrome (NS) points to a genetic predisposition. Reports on associations with certain HLA class II antigens support this hypothesis. In order to define the immunogenetic background of NS more precisely, HLA class II allele frequencies in 161 children with NS were studied by restriction fragment length polymorphism (RFLP) typing. The patient cohorts consisted of 87 children from Southwest-France and 74 from Southwest-Germany. The control group consisted of 118 French and 101 German unrelated individuals from the same geographical areas. HLA alleles were defined in patients with steroid-sensitive (SS) and steroid-resistant (SR) NS and in controls. RFLP typing revealed that the previously reported association between SSNS and HLA-DR7 is confined to the RFLP split 7.1 (DRB1*07) with a combined relative risk (RRcomb) of 6.2. HLA-DQB typing showed an increased frequency of the allele DQB2b (DQB1*0201) (RRcomb = 7.8). HLA-DQA typing showed an association of SSNS with DQA3 (DQA1*0201,0301,0302) (RRcomb = 4.1). The highest RR (16.5) for SSNS was found in German patients who carried the two DRB1 specificities 17.1 (DRB1*0301) and 7.1 (DRB1*07). All associations were stronger in SS patients with frequent relapses or steroid dependency than in non- or infrequent relapsers. SR patients exhibited no significant associations with HLA class II alleles.

Major histocompatibility complex class II antigens in steroid-sensitive nephrotic syndrome in Chinese children

Steroid-sensitive nephrotic syndrome (SSNS) has been postulated to have an immunopathogenic basis. To determine whether SSNS is associated with specific class II antigens of the major histocompatibility complex, we studied HLA-DR and DQ in 40 children with SSNS. HLA-DR7 was found in 40% of SSNS patients compared with only 11.23% of controls (P = 0.00025). HLA-DR9 occurred in 71.40% of patients with frequent relapses, compared with 27.37% of controls (P = 0.016). It seems likely that SSNS has an immunogenetic basis.

Human leukocyte antigens in childhood idiopathic nephrotic syndrome

An association of human leukocyte antigens (HLA) with idiopathic nephrotic syndrome (INS) in childhood was studied to characterize the immunogenetic background. We determined the class I antigens using the microlymphocytotoxicity test as well as class II antigens (DRB, DQB, DQA) and class III antigen (complement 4) using DNA restriction fragment length polymorphism (RFLP) in 36 children with INS. In the current study, neither the single allele in HLA class I antigen nor the single gene frequency in the class II region was significantly increased, in contrast to the results in Caucasian INS patients in whom a genetic predisposition to the HLA system, especially to HLA B8, DR3, and DR7, has been frequently reported. Also, in our data, the frequency of deletion of complement 4 gene was not different from that of the controls. These data suggest that there is a difference in immunogenetic background between Caucasian and Japanese INS patients as far as HLA is concerned.

Steroid-dependent nephrotic syndrome following renal transplantation for congenital nephrotic syndrome

A boy developed recurrent steroid-responsive nephrotic syndrome following renal transplantation for congenital nephrotic syndrome. The first episode was associated with mild tubulointerstitial rejection on kidney biopsy. Subsequent episodes showed normal histology by light microscopy and epithelial foot process fusion on electron microscopy, consistent with minimal change nephrotic syndrome. Serum analysis for soluble immune response suppressor was negative pre-nephrectomy, positive during each bout of nephrotic syndrome, and negative during each remission. This case represents de novo occurrence of steroid-sensitive minimal change nephrotic syndrome following renal transplantation for congenital nephrotic syndrome. We stress the need for histological examination of the renal allograft to diagnose rejection, recurrent disease, or de novo disease.

Human leucocyte antigens in idiopathic nephrotic syndrome in children

An association of the idiopathic nephrotic syndrome (NS) with certain human leucocyte antigens (HLA) has been reported repeatedly. The aim of this study is to characterize further the clinical and histological features of patients with NS in relation to their HLA phenotypes. HLA antigens were determined in 132 paediatric patients with NS. In 91 steroid-sensitive patients (usually associated with minimal glomerular changes), the antigen frequencies of HLA-DR3, HLA-DR7, and HLA-B8, -DR3 combined were significantly increased compared with controls. The strongest association was observed with the combined occurrence of HLA-B8, -DR3, -DR7 (relative risk 21.5). This association and that with HLA-DR3 alone were strongest in the presence of frequent relapses and steroid dependence compared with children without or with infrequent relapses. The pattern of HLA antigens was similar in the 57 steroid-sensitive patients with biopsy-proven minimal glomerular changes. In 41 children with steroid-resistant NS (usually associated with focal segmental glomerulosclerosis) a similar trend for increased antigen frequencies was found but the data were significant only for the combined occurrence of HLA-B8, -DR3 and -DR7. In all patients combined the frequency of the HLA associations was significantly lower when the age of onset was greater than 8 years compared with that of younger patients. It is concluded that the immunogenetic background of the steroid-sensitive and steroid-resistant NS is different and age-dependent.

HLA extended haplotypes in steroid-sensitive nephrotic syndrome of childhood

Idiopathic nephrotic syndrome has been postulated to have an immunopathogenic basis. To determine whether steroid-sensitive nephrotic syndrome is associated with greater than expected frequencies of specific extended haplotypes of the major histocompatibility complex, we studied genetic markers (Class I, II, III HLA alleles and glyoxalase I) in 173 subjects in 42 families of patients with nephrotic syndrome of childhood. The single allele, DQW2, was found in 72% of steroid sensitive patients compared with only 35% of the controls (P = 0.003). In half of 32 steroid sensitive, but not 10 steroid resistant, patients, one or both of two specific extended haplotypes (alleles that segregate together) were identified. The first, [HLA-A1, B8, DR3, DRW52, SCO1], occurred in 11 of 64 haplotypes, or 17%, compared to 5% of controls (P = 0.017). The other, [HLA-B44, DR7, DRW53, FC31], occurred in 10 of 64 haplotypes, 16% compared to 3.8% of controls (P = 0.014). Five patients had both haplotypes. Patients with these specific extended haplotypes had a greater frequency of relapses than did those with other haplotypes. These data provide additional support for the hypothesis that steroid-sensitive nephrotic syndrome has an immunogenetic basis.