• A 10-year-old boy is brought to the pediatric endocrinologist due to short stature. The mother reports that her son is not as tall as his classmates, and this is causing him stress. On physical exam, there is macrocephaly with frontal bossing, shortening of the arms and legs, and lumbar lordosis. Arrangements are made for genetic molecular testing.
  • Clinical definition
    • a congenital skeletal dysplasia that results in shortened extremities and macrocephaly
      • also known as dwarfism
  • Etiology
    • autosomal dominant gain-of-function mutation in fibroblast growth factor receptor (FGFR3)
  • Pathogenesis
    • constitutively active FGFR3 activity impairs chondrocyte proliferation and differentiation
      • this in turn leads to
        • impaired long bone formation (via endochondrial ossification)
        • enlarged head relative to limbs (via membranous ossification)
  • Associated findings
    • most common cause of dwarfism
    • normal life span, intelligence, and reproduction
  • Symptoms
    • asymptomatic
  • Physical exam
    • macrocephaly
    • frontal bossing
    • shortening of arms and legs
      • proximal/rhizomelic segments are more notable
    • lumbar lordosis
    • kyphoscholiosis
  • Conservative
    • monitoring, preventing, and addressing complications
      • e.g., leg bowing is managed with physical therapy

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