BACKGROUND: This article describes the neuropsychological and ophthalmicsymptoms presented by a patient with MELAS, a mitochondrial cytopathy. This rare disease is characterizedby a remitting-relapsing course against the background of a slowly progressive degenerative process.CASE REPORT: The patient is a 22-year-old Polish female, with initial onset of symptoms in 1994; theclinical diagnosis of MELAS was established in 1998, and confirmed in 2000 by the discovery of a novelmtDNA mutation. Her visual acuity fluctuates from near-normal to near-blindness, often changing dramaticallywithin a matter of weeks; the visual field has more or less steadily narrowed to lunate. Visual evokedpotentials show sporadic disturbances, while the nerve fiber layer shows significant attenuation. Theevidence points to a complex etiology, involving both cortical damage and attenuation of the optic nervesand neural pathways. A similar two-phase pattern--episodic disturbances with rapid spontaneous recoveryagainst a background of progressive deterioration--occurs in neuropsychological testing, which revealsprogressive dementia and episodic aphasia. CONCLUSIONS: The peculiar pathomechanism of MELAS resultsin simultaneous insults to various parts of the central and peripheral nervous systems, creating thecomplex and highly variable pattern seen in this patient. In clinical practice care should be taken notto overlook the possible significance of such a pattern appearing in various systems and on varying levels.

Keywords: MELAS syndrome, Magnetic Resonance Imaging, Vision Disorders, Vision Tests