Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Hereditary endotheliopathy, retinopathy, nephropathy, and stroke ?
    ### Response:
    Hereditary endotheliopathy with retinopathy, nephropathy, and stroke (HERNS) is a rare genetic condition that affects the vascular endothelium (the inner lining of the arteries and blood vessels). Specifically, the small blood vessels of the brain (microangiopathy); retina (vascular retinopathy); and kidneys are affected.
    