title: Achondroplasia with 47, XXY karyotype: a case report of the neonatal diagnosis of an extremely unusual association.
abstract: BACKGROUND
  The association of achondroplasia and Klinefelter syndrome is extremely rare. To date, five cases have been previously reported, all of them diagnosed beyond the postnatal period, and only one was molecularly characterized. We describe the first case of this unusual association diagnosed in the neonatal period, the clinical findings and the molecular studies undertaken.
  
  
  METHODS
  The boy was born at term with clinical and radiological features indicating the diagnosis of achondroplasia or hypochondroplasia combined with the prenatal karyotype of Klinefelter syndrome (47,XXY). Neonatal FGFR3 mutation screening showed that the newborn was heterozygous for the classic achondroplasia G340R mutation. Microsatellite marker analysis showed that the sex chromosome aneuploidy had arisen from a non-disjunction error in paternal meiosis I, with a recombination event in the pseudoautosomal region 1 (PAR1).
  
  
  CONCLUSIONS
  Specific mutation analysis is appropriate to confirm the clinical diagnosis of achondroplasia for appropriate diagnosis, prognosis, and genetic counseling, especially when the karyotype does not explain the abnormal prenatal sonographic findings. In the present case, a recombination event was observed in the PAR1 region, although recombinational events in paternally derived Klinefelter syndrome cases are much rarer than expected.
authors: Department of Pediatrics, Hospital Universitario Puerta de Hierro-Majadahonda, C/Manuel de Falla 1, Majadahonda, 28222, Madrid, Spain. prosmon@hotmail.com
authors: Purificación
authors: P
authors: Ros-Pérez
authors: Francisco J
authors: FJ
authors: Regidor
authors: Esmeralda
authors: E
authors: Colino
authors: Cristina
authors: C
authors: Martínez-Payo
authors: Eva
authors: E
authors: Barroso
authors: Karen E
authors: KE
authors: Heath
mesh_terms: D000130:Achondroplasia / Q000150:complications / Q000175:diagnosis* / Q000235:genetics; D005819:Genetic Markers; D005820:Genetic Testing; D006801:Humans; D007231:Infant, Newborn; D007713:Klinefelter Syndrome / Q000150:complications / Q000175:diagnosis* / Q000235:genetics; D008297:Male; D009630:Nondisjunction, Genetic; D011296:Prenatal Diagnosis; D051498:Receptor, Fibroblast Growth Factor, Type 3 / Q000235:genetics
chemical_list: D005819:Genetic Markers; C496365:FGFR3 protein, human; D051498:Receptor, Fibroblast Growth Factor, Type 3