If mri w/contrast of the brain showed lesions & have all symptoms of ms including diplopia, could i have another autoimmune disease other than ms?

Probably not: However, these lesions on MRI are suggestive of ms but they are not diagnostic. They can also be seen in lyme disease and in systemic vasculitis. It never hurts to get another neurologic opinion.

Yes: Lupus can mimic all the signs of multiple sclerosis and so can some chemical exposures.

Sjogren's Syndrome: Sjogren's is more likely than lupus to reveal ms like plaques in the brain. Both should be excluded!

See below : Antiphospholipid antibodies which are clotting antibodies which can be seen with various autoimmune diseases such as ms and create small lesions that can mimics ms on a mri. This can be easily tested for by your doctor.

?challenging?: The diagnosis of multiple sclerosis is based on history and exam, with MRI and spinal fluid studies adding supportive confirmation. Other conditions can create confusion, as has been mentioned, anti-phopholipid issues are just one category to be considered. Presume that your neurologist has done testing for other disorders, but, if not, get additional studies and start treatment.

Poss but not Prob: Some more information would be useful. For instance, if you have lesions involving the spinal cord then multiple sclerosis remains the most likely diagnosis. While it is possible to have other autoimmune disorders such as lupus or sjogren's these are statistically less likely and would present with other symptoms/signs i.e. Rash, joint involvement, dry eyes, dry mouth.... I hope this helps.