MAPPING A GENE (SRN1) TO CHROMOSOME 1Q25-Q31 IN IDIOPATHIC NEPHROTIC SYNDROME CONFIRMS A DISTINCT ENTITY OF AUTOSOMAL RECESSIVE NEPHROSIS

Idiopathic nephrotic syndrome (INS) in childhood is characterized by m assive proteinuria and minimal glomerular changes. Most patients with INS respond to steroid therapy. INS is generally regarded as a sporadi c disease with favorable outcome. We investigated a distinct subgroup of nephrosis-the familial form of steroid resistant INS (SRN). These p atients always progress to end-stage renal failure within a few years and show absence of recurrence of the disease after renal transplantat ion. The occurrence of the disorder in siblings and the high incidence of inbreeding in these families made an autosomal recessive mode of i nheritance very likely. We performed whole genome linkage analysis in nine multiplex families of European or Northern African origin. Our re sults allowed us to assign a disease locus (SRN1) to a defined chromos omal region on 1q25-1q31, thus confirming the existence of a distinct entity of autosomal recessive nephrosis. Exclusion of linkage to the e ntire region in one family proves genetic heterogeneity.