I don't know about Mastocytosis, but I do know that Lyme disease has been misdiagnosed as Multiple Slcerosis. To view the symptoms of Lyme disease, see ILADS.org. You can also watch the documentary Under Our Skin for more information regarding Lyme. Lyme can cause lesions in the brain as well, but unlike MS Lyme has a known cause and treatment. Unfortunately, current Lyme tests miss 50% of positive cases. The diagnosis of Lyme is clinical with labs as supportive.
One more thing...I just read about Mastocytosis. Apparently that affects the CD34 count. Undiagnosed Lyme disease can lower the CD 57 count.