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Table 9-6

Skeletal Dysplasias

Type of Dysplasia and Gene MutationDescriptionOutcome
Achondroplasia

  • FGFR3

  • Rhizomelic shortening of limbs

  • Frontal bossing

  • “Collar hoop” sign: rounded metaphyseal epiphyseal interface at the femur

  • Normal intelligence

  • Joint problems

  • Craniocervical junction problems

  • Obstructive sleep apnea

  • Middle ear dysfunction

  • Kyphosis

Thanatophoric dysplasia

  • FGFR3

  • Very short extremities

  • Platyspondyly—flattened vertebral ossification centers

  • Small chest

  • Telephone receiver femur (type I)

  • Cloverleaf skull (type II)

Usually lethal
Osteogenesis imperfecta

  • COL1A1

  • COL1A2

  • CRTAP/LEPRE1

  • Bone fractures

  • Irregularity and angulation to long bones

  • Decreased skull ossification

  • Irregular shape of ribs

  • Type II perinatal lethal

  • Variable features and disease severity based on the type of osteogenesis imperfecta