title: Effect of ascertainment and genetic features on the phenotype of Klinefelter syndrome.
abstract: OBJECTIVE
  To describe the Klinefelter Syndrome (KS) phenotype during childhood in a large cohort.
  
  
  METHODS
  Clinical assessment, measurement of hormonal indices of testicular function, and parent of origin of extra X chromosome were assessed in a cross-sectional study of 55 boys with KS, aged 2.0 to 14.6 years, at an outpatient center.
  
  
  RESULTS
  Mean height and body mass index SD scores (SDS +/- SD) were 0.9 +/- 1.3 and 0.4 +/- 1.4, respectively. Mean penile length and testicular volume SDS were -0.5 +/- 0.9 and -0.9 +/- 1.4. Testosterone levels were in the lowest quartile of normal in 66% of the cohort. Other features included clinodactyly (74%), hypertelorism (69%), elbow dysplasia (36%), high-arched palate (37%), hypotonia (76%), and requirement for speech therapy (69%). Features were similar in boys in whom the diagnosis was made prenatally versus boys in whom the diagnosis was made postnatally. There was no evidence for a phenotypic effect of parent of origin of the extra X chromosome.
  
  
  CONCLUSIONS
  Boys with KS commonly have reduced penile length and small testes in childhood. The phenotype in boys with KS does not differ according to ascertainment or origin of the extra X chromosome. Boys with KS may be identified before puberty by tall stature, relatively decreased penile length, clinodactyly, hypotonia, and requirement for speech therapy.
authors.affiliation: Department of Pediatrics, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: Martha P D
authors.initials: MP
authors.lastname: Zeger
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Zinn
authors.forename: Najiba
authors.initials: N
authors.lastname: Lahlou
authors.forename: Purita
authors.initials: P
authors.lastname: Ramos
authors.forename: Karen
authors.initials: K
authors.lastname: Kowal
authors.forename: Carole
authors.initials: C
authors.lastname: Samango-Sprouse
authors.forename: Judith L
authors.initials: JL
authors.lastname: Ross
mesh_terms: D000293:Adolescent; D000367:Age Factors; D001837:Body Weights and Measures; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D042341:Gonadal Hormones / Q000097:blood; D006062:Gonadotropins / Q000097:blood; D006801:Humans; D007713:Klinefelter Syndrome / Q000097:blood / Q000235:genetics* / Q000473:pathology*; D008297:Male; D010641:Phenotype
chemical_list: D042341:Gonadal Hormones; D006062:Gonadotropins