Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is characterized by a cerebral non-atherosclerotic, non-amyloid angiopathy mainly affecting the small arteries penetrating the white matter. In the brain vessels of two patients with CADASIL, abnormal patches of granular osmiophilic material have recently been described. Here we report the observation of similar granular osmiophilic material within the vessel walls of muscle and skin biopsies from a 54-year-old woman belonging to a CADASIL family, who suffered from subcortical dementia with leukoencephalopathy demonstrated on neuroimaging. Postmortem examination disclosed changes of the vessel walls in all the organs chiefly leading to cerebral lesions. Ultrastructural study showed destruction of the vascular smooth muscle cells (VSMC) and the granular osmiophilic material already found in muscle and skin biopsies in this patient. Both changes were found all along the arterial tree. The findings of this study indicate that CADASIL is a systemic vascular disease involving arterial VSMC and that the lesions are different in each organ and vessel wall, depending on their fine structure. Moreover, it emphasizes that skin and muscle biopsies might be useful for diagnosis of and research into CADASIL.