COL4A1 and cerebral small vessel disease: Notably, the clinical phenotypes of patients with COL4A1 variants are extremely variable and mutations in COL4A1 cause a wide spectrum of conditions called “COL4A1-related disorders” with eye defects, cerebral small vessel disease with or without ocular anomalies, and systemic defects, such as the hereditary angiopathy with nephropathy, aneurysms, and muscle cramps syndrome [3,4].