Renal anomalies in Alagille syndrome: a disease-defining feature.

Alagille syndrome (ALGS) is an autosomal dominant condition, primarily caused by mutations in JAGGED1. ALGS is defined by cholestatic liver disease, cardiac disease and involvement of the face, skeleton, and eyes with variable expression of these features. Renal involvement has been reported though not formally described. The objective of this study was to systematically characterize the renal involvement in ALGS. We performed a retrospective review of 466 JAGGED1 mutation-positive ALGS patients. Charts were reviewed for serum biochemistries, renal ultrasounds or other imaging, urinalysis, and clinical reports from pediatric nephrologists. The clinical data were reviewed by two pediatric hepatologists and a pediatric nephrologist. Of 466 charts reviewed we found 187 yielded evaluable renal information. Of these, 73/187 were shown to have renal involvement, representing 39% of the study cohort. Renal dysplasia was the most common anomaly seen. Genotype analysis of the JAGGED1 mutations in the patients with and without renal involvement did not reveal an association with mutation type. From the study we concluded that renal involvement has a prevalence of 39% in ALGS in our evaluable patients. Renal dysplasia is the most common renal anomaly. This finding correlates with the known role of the Notch pathway in glomerular development. Since renal disease of the type seen in ALGS can impair growth and impact liver transplantation, there is a clear need for a prospective study of renal involvement in ALGS and the development of guidelines for evaluation and management. These data also suggest that renal involvement be considered the sixth defining criterion for ALGS.

Molecular analysis of ring chromosome 20 syndrome reveals two distinct groups of patients.

BACKGROUND: The ring chromosome 20 syndrome (R20) is a rare genetic disorder associated with a refractory electroclinical epilepsy syndrome and variably expressed comorbidities of intellectual disability and dysmorphism. METHODS: To understand the structure and composition of the ring chromosome 20 (r(20)) in this patient cohort, blood specimens from 28 affected individuals were analysed by cytogenetic, fluorescence in situ hybridisation, and/or high resolution whole genome single nucleotide polymorphism array analysis. RESULTS: These studies revealed two distinct groups of patients. Group 1 (N=21) was mosaic for the r(20) and a normal cell line with no detectable deletions or duplications of chromosome 20 in either cell line. The mosaic nature of these rings suggests a postzygotic origin with formation of the ring by fusion of the telomeric regions with no apparent loss of subtelomeric or telomeric DNA. Group 2 (N=7) had non-mosaic ring chromosomes with a deletion at one or both ends of the chromosome, near the ring fusion point. The non-mosaic nature of these rings is consistent with a meiotic origin. The age of onset of seizures was significantly lower in the non-mosaic patients (group 2, median age of onset 2.1 years) than in the mosaic patients (group 1, median age of onset 6.0 years). Patients from group 2 had more extensive comorbidities. CONCLUSIONS: These studies demonstrate that r(20) is molecularly heterogeneous and formed by two distinct mechanisms, which, in turn, produce different phenotypic spectrums.