title: Abnormal brain MRI signal in 18q-syndrome not due to dysmyelination.
abstract: BACKGROUND
  18q-Syndrome is a chromosomal disorder exhibiting various symptoms arising from the central nervous system. Brain magnetic resonance imaging (MRI) of patients with this syndrome usually demonstrates abnormal white matter intensities. This is widely believed to be due to impaired myelin formation because this syndrome involves the deletion of the myelin basic protein (MBP) gene in 18q23. However, this hypothesis has not been confirmed by actual pathology because early death is unusual and autopsy rarely performed.
  
  
  METHODS
  A 6-year-old boy with ring chromosome 18 syndrome was examined by genetic analysis for the MBP gene, brain MRI, and autopsy.
  
  
  RESULTS
  Haploinsufficiency of the MBP gene was confirmed. T(2)-weighted MRI revealed diffuse high intensities throughout the cerebral white matter. Pathological examination showed the cerebral white matter to be uniformly stained by Klüver-Barrera and MBP immunohistochemical staining. Oligodendrocytes were immunoreactive for proteolipid protein and ferritin but not MBP. Electron microscopy revealed clusters of axons wrapped in compact myelin sheaths with distinct major dense lines. Holzer and immunohistochemical staining for glial fibrillary acidic protein showed extensive staining of the white matter and an increased number of glial filaments.
  
  
  CONCLUSIONS
  This pathological study demonstrated that in this disorder, the brain was well myelinated, contrary to established hypotheses about this disorder. The MRI signal abnormalities in 18q-syndrome could be attributed to gliosis and not to dysmyelination.
authors.affiliation: Department of Child Health, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan. r-tanaka@md.tsukuba.ac.jp
authors.forename: Ryuta
authors.initials: R
authors.lastname: Tanaka
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Iwasaki
authors.forename: Masaharu
authors.initials: M
authors.lastname: Hayashi
authors.forename: Junko
authors.initials: J
authors.lastname: Nakayama
authors.forename: Tatsuyuki
authors.initials: T
authors.lastname: Ohto
authors.forename: Miho
authors.initials: M
authors.lastname: Takahashi
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Numano
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Homma
authors.forename: Kenzo
authors.initials: K
authors.lastname: Hamano
authors.forename: Ryo
authors.initials: R
authors.lastname: Sumazaki
mesh_terms: D001921:Brain / Q000473:pathology*; D002648:Child; D002872:Chromosome Deletion; D025063:Chromosome Disorders / Q000473:pathology*; D002887:Chromosomes, Human, Pair 18; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D046529:Microscopy, Electron, Transmission; D009186:Myelin Sheath / Q000648:ultrastructure*