title: Biochemical and genetic analysis of 3-methylglutaconic aciduria type IV: a diagnostic strategy.
abstract: The heterogeneous group of 3-methylglutaconic aciduria type IV consists of patients with various organ involvement and mostly progressive neurological impairment in combination with 3-methylglutaconic aciduria and biochemical features of dysfunctional oxidative phosphorylation. Here we describe the clinical and biochemical phenotype in 18 children and define 4 clinical subgroups (encephalomyopathic, hepatocerebral, cardiomyopathic, myopathic). In the encephalomyopathic group with neurodegenerative symptoms and respiratory chain complex I deficiency, two of the children, presenting with mild Methylmalonic aciduria, Leigh-like encephalomyopathy, dystonia and deafness, harboured SUCLA2 mutations. In children with a hepatocerebral phenotype most patients presented with complex I deficiency and mtDNA-depletion, three of which carried POLG1-mutations. In the cardiomyopathic subgroup most patients had complex V deficiency and an overlapping phenotype with that previously described in isolated complex V deficiency, in three patients a TMEM70 mutation was confirmed. In one male with a pure myopathic form and severe combined respiratory chain disorder, based on the pathogenomic histology of central core disease, RYR1 mutations were detected. In our patient group the presence of the biochemical marker 3-methylglutaconic acid was indicative for nuclear coded respiratory chain disorders. By delineating patient-groups we elucidated the genetic defect in 10 out of 18 children. Depending on the clinical and biochemical phenotype we suggest POLG1, SUCLA2, TMEM70 and RYR1 sequence analysis and mtDNA-depletion studies in children with 3-methylglutaconic aciduria type IV.
authors.affiliation: Department of Paediatrics, Nijmegen Center for Mitochondrial Disorders, Radbound University Medical Center Nijmegen, The Netherlands.
authors.forename: Saskia B
authors.initials: SB
authors.lastname: Wortmann
authors.forename: Richard J T
authors.initials: RJ
authors.lastname: Rodenburg
authors.forename: An
authors.initials: A
authors.lastname: Jonckheere
authors.forename: Maaike C
authors.initials: MC
authors.lastname: de Vries
authors.forename: Marjan
authors.initials: M
authors.lastname: Huizing
authors.forename: Katrin
authors.initials: K
authors.lastname: Heldt
authors.forename: Lambert P
authors.initials: LP
authors.lastname: van den Heuvel
authors.forename: Udo
authors.initials: U
authors.lastname: Wendel
authors.forename: Leo A
authors.initials: LA
authors.lastname: Kluijtmans
authors.forename: Udo F
authors.initials: UF
authors.lastname: Engelke
authors.forename: Ron A
authors.initials: RA
authors.lastname: Wevers
authors.forename: Jan A M
authors.initials: JA
authors.lastname: Smeitink
authors.forename: Eva
authors.initials: E
authors.lastname: Morava
mesh_terms: D000251:Adenosine Triphosphatases / Q000172:deficiency; D001921:Brain / Q000473:pathology; D020739:Brain Diseases, Metabolic, Inborn / Q000175:diagnosis / Q000235:genetics / Q000652:urine; D009202:Cardiomyopathies / Q000175:diagnosis / Q000235:genetics / Q000652:urine; D002352:Carrier Proteins; D000074002:DNA Polymerase gamma; D004259:DNA-Directed DNA Polymerase / Q000235:genetics; D019066:Facies; D005260:Female; D005977:Glutarates / Q000652:urine*; D006801:Humans; D007231:Infant, Newborn; D008279:Magnetic Resonance Imaging / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008297:Male; D008565:Membrane Proteins / Q000172:deficiency / Q000235:genetics; D008661:Metabolism, Inborn Errors / Q000175:diagnosis* / Q000235:genetics / Q000652:urine; D028361:Mitochondrial Diseases / Q000175:diagnosis / Q000235:genetics / Q000652:urine; D024101:Mitochondrial Proteins / Q000235:genetics; D025261:Mitochondrial Proton-Translocating ATPases; D009154:Mutation; D010641:Phenotype; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics
chemical_list: D002352:Carrier Proteins; D005977:Glutarates; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D019837:Ryanodine Receptor Calcium Release Channel; C533106:TMEM70 protein, human; C022034:3-methylglutaconic acid; D000074002:DNA Polymerase gamma; D004259:DNA-Directed DNA Polymerase; C413027:POLG protein, human; D000251:Adenosine Triphosphatases; D025261:Mitochondrial Proton-Translocating ATPases; C020439:oligomycin sensitivity-conferring protein