title: Low bone mineral density in achondroplasia and hypochondroplasia.
abstract: BACKGROUND
  Achondroplasia (ACH) and hypochondroplasia (HCH) are the most common form of short-limb skeletal dysplasias caused by activated fibroblast growth factor receptor 3 (FGFR3) signaling. Although decreased bone mass was reported in gain-of-function mutation in Fgfr3 mice, both disorders have never been described as osteoporotic. In the present study, we evaluated bone mineral density (BMD) in ACH and HCH patients.
  
  
  METHODS
  We measured spinal BMD (L1-L4) in 18 ACH and four HCH patients with an average age of 19.8 ± 7.5 years (range, 10-33 years). BMD Z-score in each individual was calculated for normalizing age and gender. Correlation between body mass index (BMI) and BMD was analyzed. Moreover, BMD and Z-score were compared between ACH patients and HCH patients.
  
  
  RESULTS
  The average BMD of ACH/HCH patients was 0.805 ± 0.141 g/cm(2) (range, 0.554-1.056 g/cm(2) ), resulting in an average Z-score of -1.1 ± 0.8 (range, -2.4 to 0.6) of the standard value. A slightly positive correlation was observed between BMI and BMD (r = 0.45; P = 0.13). There was no significant difference in BMD and Z-score between ACH and HCH patients.
  
  
  CONCLUSIONS
  Spinal BMD was reduced in ACH/HCH patients, and was mildly correlated with individual BMI. We should carefully monitor BMD and examine osteoporosis-related symptoms in adolescent and adult ACH/HCH patients. © 2016 Japan Pediatric Society.
authors.affiliation: Department of Orthopaedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Matsushita
authors.affiliation: Department of Orthopaedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kitoh
authors.affiliation: Department of Orthopaedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Mishima
authors.affiliation: Department of Orthopaedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Izumi
authors.initials: I
authors.lastname: Kadono
authors.affiliation: Department of Orthopaedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sugiura
authors.affiliation: Department of Orthopaedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Sachi
authors.initials: S
authors.lastname: Hasegawa
authors.affiliation: Department of Orthopaedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Nishida
authors.affiliation: Department of Orthopaedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Ishiguro
mesh_terms: D015502:Absorptiometry, Photon; D000130:Achondroplasia / Q000175:diagnosis* / Q000235:genetics / Q000378:metabolism; D000293:Adolescent; D000328:Adult; D015519:Bone Density / Q000502:physiology*; D001842:Bone and Bones / Q000002:abnormalities* / Q000378:metabolism; D002648:Child; D004252:DNA Mutational Analysis; D004392:Dwarfism / Q000175:diagnosis* / Q000235:genetics / Q000378:metabolism; D005260:Female; D006801:Humans; D007564:Japan; D017880:Limb Deformities, Congenital / Q000175:diagnosis* / Q000235:genetics / Q000378:metabolism; D008141:Lordosis / Q000175:diagnosis* / Q000235:genetics / Q000378:metabolism; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging; D008297:Male; D009154:Mutation; D051498:Receptor, Fibroblast Growth Factor, Type 3 / Q000235:genetics / Q000378:metabolism; D055815:Young Adult
chemical_list: C496365:FGFR3 protein, human; D051498:Receptor, Fibroblast Growth Factor, Type 3
keywords: achondroplasia; bone mineral density; fibroblast growth factor receptor 3; hypochondroplasia; osteoporosis