title: Delayed myelination is not a constant feature of Allan-Herndon-Dudley syndrome: report of a new case and review of the literature.
abstract: BACKGROUND
  Allan-Herndon-Dudley syndrome is an X-linked condition caused by mutations of the monocarboxylate transporter 8 gene. This syndrome is characterized by axial hypotonia, severe mental retardation, dysarthria, athetoid movements, spastic paraplegia, and a typical thyroid hormone profile. In most of the cases reported so far, brain magnetic resonance imaging showed delayed myelination of the central white matter and this finding greatly affects the diagnosis of the syndrome.
  
  
  METHODS
  We present a new case studied with magnetic resonance imaging and spectroscopy and we reviewed all the articles published between 2004 and 2012 containing information on brain neuroimaging in this syndrome. An Italian boy, showing a classical phenotype of the syndrome, was diagnosed at 17months of age. Genetic analysis revealed a new frameshift mutation of the monocarboxylate transporter 8 gene. His brain magnetic resonance imaging and spectroscopy, performed at the age of 14months, were normal.
  
  
  CONCLUSIONS
  Among the 33 cases reported in the literature, 3 cases had normal neuroimaging and in 7 of 14 cases, having a longitudinal follow-up, the initial finding of delayed myelination gradually improved. Our case and the review of the pertinent literature suggest that Allan-Herndon-Dudley syndrome should be suspected in males with the typical neurological and thyroid profile, even in cases with normal brain myelination.
authors.affiliation: Pediatric Endocrinology Unit, Department of Woman's and Child's Health, University Hospital of Padua, Padua, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Azzolini
authors.affiliation: Child Neurology Unit, Department of Woman's and Child's Health, University Hospital of Padua, Padua, Italy.
authors.forename: Margherita
authors.initials: M
authors.lastname: Nosadini
authors.affiliation: Pediatric Endocrinology Unit, Department of Woman's and Child's Health, University Hospital of Padua, Padua, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Balzarin
authors.affiliation: Child Neurology Unit, Department of Woman's and Child's Health, University Hospital of Padua, Padua, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Sartori
authors.affiliation: Child Neurology Unit, Department of Woman's and Child's Health, University Hospital of Padua, Padua, Italy.
authors.forename: Agnese
authors.initials: A
authors.lastname: Suppiej
authors.affiliation: Institute of Neuroradiology, University Hospital of Padua, Padua, Italy.
authors.forename: Rodica
authors.initials: R
authors.lastname: Mardari
authors.affiliation: Pediatric Endocrinology Unit, Department of Woman's and Child's Health, University Hospital of Padua, Padua, Italy.
authors.forename: Nella Augusta
authors.initials: NA
authors.lastname: Greggio
authors.affiliation: Child Neurology Unit, Department of Woman's and Child's Health, University Hospital of Padua, Padua, Italy. Electronic address: irene.toldo@unipd.it.
authors.forename: Irene
authors.initials: I
authors.lastname: Toldo
mesh_terms: D001921:Brain / Q000473:pathology; D016368:Frameshift Mutation; D006801:Humans; D007223:Infant; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D038901:X-Linked Intellectual Disability / Q000175:diagnosis* / Q000235:genetics*; D027501:Monocarboxylic Acid Transporters / Q000235:genetics*; D009123:Muscle Hypotonia / Q000175:diagnosis* / Q000235:genetics*; D009133:Muscular Atrophy / Q000175:diagnosis* / Q000235:genetics*; D009186:Myelin Sheath / Q000473:pathology*; D027981:Symporters
chemical_list: D027501:Monocarboxylic Acid Transporters; C090735:SLC16A2 protein, human; D027981:Symporters
keywords: Allan–Herndon–Dudley syndrome; Brain magnetic resonance imaging; Central hypotonia; Monocarboxylate transporter 8; SLC16A2 gene; Thyroid hormone