The normal function of the TREX1 gene is to provide instructions for making the 3-prime repair exonuclease 1 enzyme. This enzyme is a DNA exonuclease, which means it trims molecules of DNA by removing DNA building blocks (nucleotides) from the ends of the molecules. In this way, it breaks down unneeded DNA molecules or fragments that may be generated during genetic material in preparation for cell division, DNA repair, cell death, and other processes. Changes (mutations) to the TREX1 gene can result in a range of conditions, one of which is RVCL. The mutant TREX1 protein is produced and mislocalized. Haploinsufficiency of TREX1 does not explain the disease, since the parents of patients with Aicairdi-Goutieres syndrome, a disease characterized by insufficient TREX1 activity, are completely healthy with only one functional TREX1 allele. Different mutations in the TREX1 gene have also been identified in people with disorders involving the immune system. These disorders include a chronic inflammatory disease called Aicardi-Goutieres syndrome, as well as systemic lupus erythematosus (SLE), including a rare form of SLE called chilblain lupus that mainly affects the skin. Those diseases, which are inflammatory, may have a completely distinct mechanism compared with that of RVCL. The TREX1 gene is located on chromosome 3: base pairs 48,465,519 to 48,467,644

Pathogenesis
The main pathologic process centers on small blood vessels that prematurely "drop out" and disappear. The retina of the eye and white matter of the brain appear to be among the most sensitive to this pathologic process.
Retinal vasculopathy with cerebral leukocencephalopathy and systemic manifestations (RVCL or RVCL-S, also previously known as retinal vasculopathy with cerebral leukodystrophy, RVCL; or cerebroretinal vasculopathy, CRV; or hereditary vascular retinopathy, HVR; or hereditary endotheliopathy, retinopathy, nephropathy, and stroke, HERNS) is an inherited condition resulting from a frameshift mutation in the C-terminal region of the TREX1 gene. This disease affects  small blood vessels, leading to damage of multiple organs including but not limited to the retina and the white matter of the central nervous system. Patients with RVCL develop vision loss, brain lesions, strokes, brain atrophy, and dementia. Patients with RVCL also exhibit other organ involvement, including kidney, liver, gastrointestinal tract, thyroid, and bone disease. Symptoms of RVCL commonly begin between ages 40 and 50, although sometimes disease onset occurs earlier or later. The overall prognosis is poor, and death can sometimes occur within 5 or 10 years of the first symptoms appearing, although patients sometimes live about 20 years after initial symptoms. Clinical trials are underway, as are efforts to develop personalized medicines for patients with RVCL. Presentation
For most patients, disease onset is between ages 35 and 55. Earliest onset is usually not before age 35. Late onset is usually not after age 55. RVCL affects multiple organs. All patients develop brain and eye disease, leading to disability, vision loss, and premature death. All patients with RVCL develop kidney and liver disease, with elevated alkaline phosphatase. Some patients develop bone lesions (osteonecrosis) as well as hypothyroidism. Sometimes patients also develop gastrointestinal symptoms or bleeding.