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Introduction:Leigh syndrome is a neurodegenerative disorder, characterized by symmetricallesion of basal ganglia, thalamus, and brainstem.  Dysfunction of the respiratory chain is themain cause of the disease, but no definite metabolic derangement is evident in40-65%.  We present a case of 3-methylglutaconicaciduria with clinical and neuroradiological findings of Leigh syndrome.Case:A Four-year-old boy was born from non-related healthy parents.  Nystagmus was noticed at 6 months.  At 12 months, he showed developmentalregression with hypotonia, nystagmus, and choreoathetosis.  Brain MRI showed symmetrical hyper intensityof the basal ganglia and substantia nigra on T2WI, FLAIR, and DWI.  Cerebrospinal fluid test showed increasedlevel of lactate and pyruvate (25.4mg/dl and 2.21 mg/dl, respectively).  Urinary organic acid profiles showed mildincrease of 3-hydroxyisobutyrate.  Respiratorychain complex was normal in muscle biopsy.  Exon sequences of pyruvate dehydrogenasecomplex E1α showed no mutation.  We diagnosed Leigh syndrome, and treated withvitamins, pyruvate，and ketogenic nutrition.  But triggered by febrile illness, psychomotordisability, hypotnia, dystonic movement, visual loss, deafness, and breath holdingspells progressed.  At age 2, urinemetabolomic analysis and urine organic analysis showed mild elevation of 3-methylglutaconicacid.  Fillipin staining performed infibroblasts, showed mild accumulation of free cholesterol.  We considered it to be 3-methylglutaconicaciduria with sensori-neural deafness, encephalopathy, and Leigh-like syndrome (MEGDELsyndrome).  Now sequence analysis of SERAC1 is being performed.  Discussion: Leigh syndrome is caused by heterogeneous defects in energymetabolism.  3-metylglutaconic aciduria isa rare cause.  Repeated urinary analysisand fillipin staining represent the diagnosis.

3-methylglutaconic aciduria; Leigh syndrome, MEGDEL