P1818CLINICAL AND MOLECULAR CHARACTERISTICS OF CHILDREN WITH WT-1-ASSOCIATED STEROID-RESISTANT NEPHROTIC SYNDROME

Abstract

Abstract Background and Aims The Wilms tumor suppressor gene 1 (WT1) (MIM 607102) has an important role in renal and gonadal development. WT1 mutations was found to be associated with a large spectrum of phenotypes with autosomal-dominant inheritance, including Wilms tumor, Denys-Drash syndrome (DDS), Frasier syndrome (FS), and isolated steroid-resistant nephrotic syndrome (SRNS). The aim of the study was to investigate clinical and molecular characteristics in children with WT1-associated SRNS. Method Retrospective analysis of phenotype and genotype of six children (3M/3F) with SRNS and heterozygous WT1 mutations was performed. Karyotypes were available in all patients. Data on renal histology had three subjects with FS. The median follow-up period was 35.5 (IQR: 20.0; 57.5) months. WT1 mutations identified by direct Sanger sequencing (n=3) and next generation sequencing (n=3). Results The median age at onset of WT1-associated SRNS was 10.0 (IQR: 5.5; 22.5) months. 4/6 (66.7%) patients presented with infantile nephrotic syndrome and 2/6 (33.3%) with SRNS. Arterial hypertension was determined in 4/6 (66.7%) of individuals. Among children with WT1-associated SRNS 3/6 (50%) patients had DDS (2M/1F) and 3/6 (50%) subjects had FS (1M/2F). Children with DDS had Wilms tumor in 2/3 (66.7%) of cases and gonadal dysgenesis with hypospadias in 1/3 (33.3%) of children. Causative mutations were identified in all three patients with DDS, including 2 earlier described c.1384C>T in exon 9 and c.1098 + 1G>A in intron 6 in WT1 gene, and one novel mutation с.1378Т>G in exon 9. All DDS children had decreased eGFR to CKD stage 2-3 in two patients aged 7 and 11 years and ESKD in one child at the age of 2 years. All 3 patients with FS had focal segmental glomerulosclerosis on biopsy. Two phenotypic girls with FS had karyotype 46, XY and presented with pseudohermaphroditism. The same earlier described splice site mutation c.1432 + 5G>A in intron 9 in WT1 gene was identified in both cases. One boy with FS had typical male chromosome pattern (46, XY) and gonadal dysgenesis. Splice site mutation c.1432 + 4C>T in intron 9 in WT1 gene was found in the child. Nobody of patients with FS developed gonadoblastoma. Progression to CKD was found in all three cases with FS, including CKD stage 2-3 in two subjects aged 5 and 15 years and ESKD in one phenotypically girl with sex reversal developed at the age of 8 years. Conclusion We found that children with WT1-associated SRNS had a wide spectrum of renal and extrarenal phenotypes concerning the development of urogenital system and Wilms tumor with high risk of progression to CKD during childhood. Their phenotypes are clearly associated with the type and location of WT1 mutations led to DDS or FS. Genetic WT1 diagnostics is important in all children with SRNS for early detection, optimal treatment, tumor prevention and prognosis.