Please let me know if there is a vascular disease that might get misdiagnosed as ms?

Actually several: A classic is the genetic disorder cadasil, but lupus may result in both cerebritis and arteritis. The differential diagnosis in ms is broad and can also include disorders which are not exactly vascular, but should be considered such as hiv, syphilis, lyme disease, pernicious anemia, and perhaps melas. Theoretically, a series of small lacunar strokes could mimic ms course, but easy to sort out.

Yes- there are: One example of this is a rare condition called cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). This condition can be tested for by NOTCH3 genetic testing or by a special skin biopsy. One thing unique about this condition is that white matter abnormalities son MRI appear confluent and are located in the poles of the temporal lobes.