title: Homozygosity for CCTG mutation in myotonic dystrophy type 2.
abstract: Myotonic dystrophy type 2 (DM2) is caused by a dominantly transmitted CCTG repeat expansion in intron 1 of the zinc finger protein 9 (ZNF9) gene on chromosome 3q. DM2 patients with two mutant alleles have not been reported so far. In one large consanguineous family from Afghanistan, we found three homozygotes for the DM2 mutation. The oldest patient was clinically more severely affected, compared with the two younger homozygotes, but for the clinical course of symptoms all three homozygotes were within the range expected for heterozygotes. Further investigations, such as mutation repeat length, muscle histology, anti-muscleblind-like 1 stainings or brain imaging studies, at least at short-term observation, showed no differences between heterozygotes and homozygotes. Twenty of 24 children, aged 2-21 years, were available for clinical examination. None of these children have signs or symptoms of disease until the age of 18 years. Homozygosity for the DM2 expansion does not seem to alter the disease phenotype as compared with the heterozygous state.
authors.affiliation: Friedrich Baur Institute, Department of Neurology, Ludwig Maximilians University, Ziemssenstr. 1a, D-80336 Munich, Germany. bschoser@fbs.med.uni-muenchen.de
authors.forename: Benedikt G H
authors.initials: BG
authors.lastname: Schoser
authors.forename: Wolfram
authors.initials: W
authors.lastname: Kress
authors.forename: Maggie C
authors.initials: MC
authors.lastname: Walter
authors.forename: Birgit
authors.initials: B
authors.lastname: Halliger-Keller
authors.forename: Hanns
authors.initials: H
authors.lastname: Lochmüller
authors.forename: Kenneth
authors.initials: K
authors.lastname: Ricker
mesh_terms: D000293:Adolescent; D000328:Adult; D000346:Afghanistan; D015139:Blotting, Southern; D002648:Child; D002675:Child, Preschool; D002893:Chromosomes, Human, Pair 3 / Q000235:genetics; D042622:DNA Repeat Expansion; D005260:Female; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology; D009223:Myotonic Dystrophy / Q000235:genetics* / Q000473:pathology; D010375:Pedigree; D010641:Phenotype; D016133:Polymerase Chain Reaction / Q000379:methods; D016601:RNA-Binding Proteins / Q000235:genetics*; D016335:Zinc Fingers / Q000235:genetics
chemical_list: C433227:CNBP protein, human; D016601:RNA-Binding Proteins