Late onset Leigh syndrome mimicking central nervous system vasculitis

Leigh syndrome is typically a disorder of infancy and early childhood. Only a few patients with late onset Leigh syndrome have been reported [1]. The disorder is most likely underdiagnosed in adolescents and adults. In the past, many adults with Leigh syndrome were misdiagnosed with multiple sclerosis [2,3].Here, we describe a 17 year old girl with Leigh syndrome mimicking as central nervous system vasculitis. This patient with history of learning disability developed blurring of vision and dysphagia followed by tiredness, fever, chest pain, shortness of breath, and intermittent double vision. On examination, she had tachycardia, hypertension, and anisocoria. MRI of the brain showed lesions in the right brainstem and the left basal ganglia concerning for stroke. CT angiography showed diffuse, subtle irregularities of intracranial arteries suggesting vasculitis. A detailed work for vasculitis was unremarkable except a high ESR at 33. She was treated with intravenous pulse methylprednisone followed by oral steroids. Her symptoms improved and steroids were tapered. However, she developed irregular breathing and poor respiratory effort during the taper. She developed restricted lateral gaze bilaterally and mild vertical nystagmus in upward gaze. A repeat MRI of the brain showed small foci of T2 hyperintensities bilaterally within the basal ganglia, midbrain, posterior pons, and medulla (Fig. 1). This worsening in symptoms was considered secondary to a flare up of vasculitis due to steroid tapering. Aggressive immunosuppressive therapies were instituted but the patient had no improvement. Bilateral carotid and left vertebral artery angiogram was normal. Based upon repeat MRI findings, a mitochondrial etiology was suspected. Respiratory chain enzyme analysis on skeletal muscle biopsy showed decreased activity of all complexes except complex II. A next generation sequencing panel for mitochondrial DNA and nuclear genes implicated in mitochondrial disorders, performed on skeletal muscle detected c.626 C N T (p.R181Sfs*5) mutations in homozygous state in MTFMT gene. In a recent study, pathogenic mutations in MTFMT gene were found in 11 patients with Leigh syndrome [4]. The age at onset of symptoms in the cohort ranged from birth to 17 years. The most common pathogenic mutation in MTFMT, c.626 C N T, was