Familial steroid-sensitive nephrotic syndrome in Southern Israel: clinical and genetic observations

Reports on genetically informative steroid-responsive (sensitive) idiopathic nephrotic syndrome (SSNS) families are lacking. We studied an extended SSNS Bedouin (B) family with a high rate of consanguinity. The clinical presentation and steroid response of its 11 affected individuals were similar to those of sporadic SSNS (spontaneous remission towards puberty and minimal change disease by kidney biopsy). Genome-wide linkage analysis, using a 382 microsatellite-markers mapping set and additional markers adjacent to 80 candidate genes of the index family, did not support linkage to any chromosomal locus. Retrospective analysis of all additional children with SSNS treated by our institution in the past 20 years (n=96, 50% of them of Jewish origin) revealed another five non-related B families with 2-3 first-degree cousins affected with SSNS in each. The overall familial SSNS rate among the B population (excluding the index family) was 28%, compared with 4% among Jews (Js) (OR 1.8-64, P < 0.005). There were more Bs with simple SSNS than there were Js (71% and 40%, respectively; OR 3.58, 95% CI 1.41-9.23, P < 0.01). In summary, SSNS in this index family was not linked to any of the presently known chromosomal loci nor predicted to be caused by mutation in any one of a list of genes associated with nephrotic syndrome (NS). The presence of other B families affected by SSNS supports the role for susceptibility genes enrichment, exposing highly consanguineous populations to an increased incidence of SSNS.