053 GLUT-1 deficiency presenting as dopa-responsive dystonia: an atypical phenotype of a rare disease

Abstract

IntroductionThe SLC2A1 gene encodes the glucose transporter GLUT1, responsible for normal glucose transport across the blood-brain barrier. Mutations in this gene have classically been associated with an epileptic encephalopathy referred to as GLUT-1 Deficiency Syndrome, which typically presents with early-onset refractory epilepsy, developmental delay and complex movement disorders.1 2 More recently, SLC2A1 variants have been identified in patients with paroxysmal exercise-induced dyskinesia (PED), with or without a history of epilepsy.3 4 Response to medication is typically poor; however, both seizures and dyskinesia may improve following implementation of a ketogenic diet.5 A single case of levodopa responsiveness has previously been described in a subject with SLC2A1 mutation and PED.5Methods and resultsWe describe a 47-year-old female with mild intellectual disability since childhood but no history of epilepsy, who developed episodic dystonia affecting the lower limbs in her early 20’s. A clinical diagnosis of dopa-responsive dystonia was made following a marked, sustained response to levodopa. There was no significant family history. In her 40’s she developed breakthrough dystonia with exertion and choreiform movements affecting the fingers and face. A subsequent dystonia panel identified a heterozygous variant c.[1199G>T];[=] (p.Arg400Leu) in the SLC2A1 gene. Cerebrospinal fluid glucose concentration was low (2.0 mmol/L). She declined a trial of a ketogenic diet.SLC2A1 variants are associated with PED; however, response to levodopa has not been widely reported.ConclusionIt is becoming increasingly evident that the phenotypic presentations of GLUT1 deficiency are diverse, and SLC2A1 testing should be considered in a broader range of patients.ReferencesWang, D, Kranz-Eble P, De Vivo DK. Mutational analysis of GLUT1 (SLC2A1) in Glut-1 Deficiency Syndrome. Human Mutation 2001;16:224–231.Klepper J, Leiendecker B. GLUT1 deficiency syndrome – 2007 update. Developmental Medicine & Child Neurology 2007;49:707–716.Schneider SA, Paisan-Ruiz C, Garcia-Gorostiaga I, Quinn NP, Weber YG, et al. GLUT1 gene mutations cause sporadic paroxysmal exercise-induced dyskinesias. Mov Disord 2009;24(11):1684–1696.Suls A, Dedeken P, Goffin K, Van Esch H, Dupont P. Paroxysmal exercise-induced dyskinesia and epilepsy is due to mutations in SLC2A1, endoding the glucose transporter GLUT1. Brain 2008;131:1831–1844.Baschieri F, Batla A, Erro R, Ganos C, Cordivari C, Bhatia KP. Paroxysmal exercise-induced dystonia due to GLUT-1 mutation can be responsive to levodopa: a case report. J Neurol 2014;261:615–616.