This white matter disease is due to very gradual loss of blood supply. Our brain is composed of two type of matters; white matter and grey matter. Changes in the brain can be generalized, affecting the white matter as well as grey matter. When any particular change in the brain affects either of two matter predominantly, as in your case, it is white matter, it is termed as white matter disease.
Your white matter changes, as I mentioned, is due to chronic microvascular ischemic changes. When we age, gradually blood supply to all organs, including the brain, gets decreased. These are termed as degenerative changes. These changes are very gradual thus the term chronic. When they are not in the major blood vessels, and affect those blood vessels only, which are so tiny, that can't be visualized, they are termed microvascular. Ischemic is loss/decrease of blood supply.
So it is not dangerous. As they are age related changes. Good news is that they have not progressed much from 5/11/207. The treatment of this is to take care of diabetes or blood pressure or abnormal lipid profile, if one suffers with these problems. Some neurologists may prescribe multivitamins.
Please feel free for your follow up questions.