Relapsing remitting multiple sclerosis in progressive external ophthalmoplegia: A report of two cases.

Evidence from genetic and pathologic studies suggests that mitochondrial dysfunction occurs in multiple sclerosis (MS). Furthermore, cases of MS have been reported in patients with mitochondrial disease. The phenotypic range of mitochondrial illness associating with MS is not yet well defined. In this report, we highlight two cases of patients with confirmed genetic mutations responsible for progressive external ophthalmoplegia who independently meet McDonald criteria for MS. Better characterization of the range of mitochondrial disease associated with MS may improve our understanding of MS disease pathophysiology.