A further case of familial ring chromosome 20 mosaicism - molecular characterization of the ring and review of the literature.

Ring chromosome 20 syndrome is a rare chromosomal disorder characterized by childhood-onset drug-resistant epilepsy, behavioral problems and variable cognitive impairment. While most cases occur sporadically, parent-to-child transmission of ring 20 mosaicism has only been reported in a few exceptional families. We identified a further family with mother-to-child transmission of ring 20 mosaicism. Detailed characterization of the ring chromosome showed a complete ring with preserved telomere repetitive sequences. SNP genotyping excluded mosaic uniparental disomy and indicated that the chromosome was transmitted without recombination from mother to child. These results corroborate the findings of a previous study and support the hypothesis that inherited mosaicism is due to transmission of an unstable chromosome either prone to ring opening or to ring re-formation.

Canavan disease: a novel mutation.

Canavan disease, an autosomal recessive inherited leukodystrophy caused by an aspartoacylase deficiency, is common among children of Ashkenazi Jewish descent. We report on a non-Jewish female infant who presented at age 6 months with progressive macrocephaly and developmental delay. A sequence analysis of the aspartoacylase gene revealed compound heterozygosity for a known mutation and for the mutation c.432G>A in exon 2, which has not yet been described in Canavan disease.