Mutations in NOTCH3 are the cause of cerebral autosomal dominant arteriopathy 
with subcortical infarcts and leukoencephalopathy (CADASIL), a hereditary 
angiopathy causing stroke and vascular dementia. All CADASIL mutations 
identified so far result in the loss or gain of one cysteine residue within 
epidermal growth factor (EGF)-like repeat domains. Here an in-frame deletion 
causing a loss of three cysteine residues within EGF repeat 6 is reported. These 
data are consistent with the hypothesis that the change toward an odd number of 
cysteine residues within a given EGF repeat and therefore an unpaired, reactive 
cysteine residue is the common and critical molecular event in CADASIL.