Histopathologic Analysis of Cerebral Autosomal Recessive Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CARASIL): A Report of a New Genetically Confirmed Case and Comparison to 2 Previous Cases.

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is a nonhypertensive hereditary cerebral small vessel disease that is caused by mutations in a single gene, HTRA1. The HTRA1 protein normally represses transforming growth factor-β (TGF-β) signaling and its mutations result in vascular changes. Ten homozygous, 1 compound heterozygous, and 1 homozygous frameshift mutation have been identified in the HTRA1 gene of patients with genetically confirmed CARASIL. However, few studies have compared neuropathologic findings in patients with the same or different mutations in HTRA1. We analyzed histopathologic alterations in 3 autopsied patients with genetically confirmed CARASIL: 2 of them had the HTRA1 p.R302X mutation and 1 had the HTRA1 p.A252T mutation. All 3 had similar cerebral arteriopathy showing myointimal proliferation, multi-layering and splitting of elastic laminae, and marked loss of medial smooth muscle cells. One CARASIL patient with the p.R302X mutation had atherosclerosis-like intimal thickening and arteriolosclerosis in the arteries of visceral organs, indicating that atherosclerotic changes are not confined to the intracranial vasculature but can occur throughout the body. CARASIL is a unique hereditary disease that shows similar neuropathology, systemic vascular pathology, and other TGF-β1-related pathology associated with HTRA1 mutation.