A 44-year-old Albanian male was consulted and diagnosed with dementia. His magnetic resonance imaging suggested diffuse white matter changes. The suspicion of cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) was raised, and a genetic analysis confirmed such a suspicion through uncovering a pathogenic mutation at the level of exon 4 (c.475C>T) of chromosome 19. The patient came from a large family of 13 children, all of whom underwent clinical, genetic, and imaging examination. The pathogenic mutation was found present only in his eldest sister (50 years old), and she presented also very suggestive signs of CADASIL in her respective imaging study, but without any clinically significant counterpart. All other siblings were free from clinical and radiological signs of the disorder. Our opinion was that we were dealing with a mutation showing a very low level of penetrance, with only two siblings affected in a large Albanian family with 13 children.