title: Mosaic Turner syndrome and hyperinsulinaemic hypoglycaemia.
abstract: BACKGROUND
  A common and well recognised feature of Turner's syndrome (partial or total monosomy X) is impaired glucose tolerance or type 2 diabetes mellitus. A small percentage of patients with Turner's syndrome have a complex mosaic karyotype with atypical clinical features and mental retardation. METHODS/PATIENT: We report the first case of a child with a complex mosaic Turner genotype and hyperinsulinaemic hypoglycaemia responsive to diazoxide therapy.
  
  
  RESULTS
  Cytogenetic analysis showed four cell lines: one with 45,X; the others with an additional small ring chromosome, a small marker chromosome, and both the ring and marker chromosomes, respectively. FISH studies showed the abnormal chromosomes to originate from an X. The X inactivation locus (XIST) was present in the ring, but not in the marker chromosome.
  
  
  CONCLUSIONS
  The recognition of hypoglycaemia in children with atypical Turner's syndrome is important as persistent hypoglycaemia may lead to brain damage in addition to the risk of mental retardation. Further studies are required to understand whether the mosaic over--or underexpression of unidentified X chromosome gene(s) in the pancreatic beta-cells leads to hyperinsulinaemic hypoglycaemia.
authors.affiliation: London Centre for Paediatric Endocrinology and Metabolism, Great Ormond Street Hospital for Children NHS Trust and The Institute of Child Health, London, UK.
authors.forename: Haya
authors.initials: H
authors.lastname: Alkhayyat
authors.forename: Henrik B T
authors.initials: HB
authors.lastname: Christesen
authors.forename: James
authors.initials: J
authors.lastname: Steer
authors.forename: Helen
authors.initials: H
authors.lastname: Stewart
authors.forename: Klaus
authors.initials: K
authors.lastname: Brusgaard
authors.forename: Khalid
authors.initials: K
authors.lastname: Hussain
mesh_terms: D002869:Chromosome Aberrations; D041321:Chromosomes, Human, X; D003981:Diazoxide / Q000627:therapeutic use; D005260:Female; D006801:Humans; D006946:Hyperinsulinism / Q000150:complications / Q000188:drug therapy / Q000473:pathology*; D007003:Hypoglycemia / Q000150:complications / Q000188:drug therapy / Q000473:pathology*; D007231:Infant, Newborn; D007621:Karyotyping; D009030:Mosaicism; D016896:Treatment Outcome; D014424:Turner Syndrome / Q000150:complications / Q000235:genetics* / Q000473:pathology*; D014665:Vasodilator Agents / Q000627:therapeutic use; D049951:X Chromosome Inactivation / Q000235:genetics
chemical_list: D014665:Vasodilator Agents; D003981:Diazoxide