title: Isolated complex I deficiency in children: clinical, biochemical and genetic aspects.
abstract: We retrospectively examined clinical and biochemical characteristics of 27 patients with isolated enzymatic complex I deficiency (established in cultured skin fibroblasts) in whom common pathogenic mtDNA point mutations and major rearrangements were absent. Clinical phenotypes present in this group are Leigh syndrome (n = 7), Leigh-like syndrome (n = 6), fatal infantile lactic acidosis (n = 3), neonatal cardiomyopathy with lactic acidosis (n = 3), macrocephaly with progressive leukodystrophy (n = 2), and a residual group of unspecified encephalomyopathy (n = 6) subdivided into progressive (n = 4) and stable (n = 2) variants. Isolated complex I deficiency is one of the most frequently observed disturbance of the OXPHOS system. Respiratory chain enzyme assays performed in cultured fibroblasts and skeletal muscle tissue in general reveal similar results, but for complete diagnostics we recommend enzyme measurements performed in at least two different tissues to minimize the possibility of overlooking the enzymatic diagnosis. Lactate levels in blood and CSF and cerebral CT/MRI studies are highly informative, although normal findings do not exclude complex I deficiency. With the discovery of mutations in nuclear encoded complex I subunits, adequate pre- and postnatal counseling becomes available. Finally, considering information currently available, isolated complex I deficiency in children seems to be caused in the majority by mutations in nuclear DNA.
authors.affiliation: Nijmegen Center for Mitochondrial Disorders (NCMD), Department of Pediatrics, University Hospital Nijmegen, Nijmegen, The Netherlands.
authors.forename: J L
authors.initials: JL
authors.lastname: Loeffen
authors.forename: J A
authors.initials: JA
authors.lastname: Smeitink
authors.forename: J M
authors.initials: JM
authors.lastname: Trijbels
authors.forename: A J
authors.initials: AJ
authors.lastname: Janssen
authors.forename: R H
authors.initials: RH
authors.lastname: Triepels
authors.forename: R C
authors.initials: RC
authors.lastname: Sengers
authors.forename: L P
authors.initials: LP
authors.lastname: van den Heuvel
mesh_terms: D002648:Child; D004272:DNA, Mitochondrial / Q000235:genetics; D004579:Electron Transport / Q000235:genetics; D042967:Electron Transport Complex I; D005260:Female; D006801:Humans; D008297:Male; D008661:Metabolism, Inborn Errors / Q000175:diagnosis / Q000201:enzymology* / Q000235:genetics* / Q000473:pathology; D009154:Mutation / Q000235:genetics*; D009247:NADH, NADPH Oxidoreductases / Q000172:deficiency* / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype
chemical_list: D004272:DNA, Mitochondrial; D009247:NADH, NADPH Oxidoreductases; D042967:Electron Transport Complex I