Mimicry between mitochondrial disorder and multiple sclerosis.

Under certain conditions or at certain stages of the disease course, multiple sclerosis (MS) and mitochondrial disorder (MID) may be differential diagnoses and thus may be confused with each other. In a 30 years old female MS was diagnosed at age 16 year upon recurrent sensory disturbances of the right lower leg, an "inflammatory" cerebrospinal fluid, and a cerebral MRI with multiple non-enhancing white matter lesions. Steroids were repeatedly given but because of rapid deterioration treatment was switched to interferon and mitoxantrone, without improvement. Fourteen years after onset the patient additionally presented with a history of rhabdomyolysis, hypothyroidism, ophthalmoparesis, anarthria, tetraspasticity, tetraparesis, and joint contractures. After MID had been diagnosed in her mother she was re-evaluated and elevated resting lactate, axonal polyneuropathy, and empty sella were additionally found. Muscle biopsy revealed myophagy, fat deposition, and type-II predominance, and biochemical investigations showed a deficiency of complex I and IV of the respiratory chain. MID was diagnosed also in the index patient. It is concluded that even if CSF investigations or imaging studies suggest MS, differentials such as MIDs need to be excluded before prescribing medication possibly toxic to a MID. An "inflammatory CSF" may also occur in MIDs.