What factors determine phenotype of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL)? Considerations in the context of a novel pathogenic R110C mutation in the NOTCH3 gene

We report patients from a Polish family with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) who possess a novel heterozygous R110C mutation in exon 3 of the NOTCH3 gene leading to stereotypical cysteine loss. The proband had only seizure attacks and her magnetic resonance imaging (MRI) showed very numerous hyperintense foci in the cerebral white matter in a location characteristic of CADASIL. Distinctive ultrastructural assessment of vessels from skin-muscle biopsy revealed only mild degenerative changes but relatively numerous homogeneous deposits of granular osmiophilic material (GOM). In the other symptomatic family members with the same mutation ischaemic strokes were present but not epilepsy. In the proband's affected brother at a similar age, the brain MRI was normal but vessels showed pronounced degenerative changes and irregular GOM deposits. The present report not only extends the list of known pathogenic mutations responsible for CADASIL but also emphasizes clinical and morphologic variability among family members with the same NOTCH3 mutation, suggesting that probably additional factors, not only mutations, may influence the disease phenotype.