Differential diagnosis of skeletal dysplasias

• Achondroplasia
• Asphyxiating thoracic dystrophy
• Campomelic dysplasia
• Chondrodysplasia punctata
• Chondroectodermal dysplasia
• Diastrophic dysplasia
• Mucopolysaccharidoses
• Pyknodysostosis
• Spondyloepiphyseal dysplasia
• Thanatophoric dysplasia

Approach to the DDX of skeletal dysplasias:

• Types of limb shortening
  — Rhizomelic – proximal appendicular skeleton – humerus, femur
  — Mesomelic – middle appendicular skeleton – radius-ulna, tibia-fibula
  — Acromelic – distal appendicular skeleton – metacarpals, metatarsals, phalanges
  — Micromelic – entire appendicular skeleton
• Lethal skeletal dysplasias due to short ribs leading to thoracic dysplasia
  — Rhizomelic – thanatophoric dysplasia, achondrogenesis
  — Mesomelic – campomelic dysplasia
  — Acromelic – asphyxiating thoracic dystrophy, chondroectodermal dysplasia, short rib polydactyly
• Non-lethal skeletal dysplasias
  — Rhizomelic – achondroplasia, chondrodysplasia punctata, diastrophic dysplasia, spondyloepiphyseal dysplasia
  — Mesomelic –
  — Acromelic – pyknodysostosis
• Shortened body portion
  — Short limbed, normal trunk
  — Rhizomelic – achondroplasia
  — Mesomelic –
  — Acromelic –
  — Short trunk, normal limbed – chondrodysplasia punctata, spondyloepiphyseal dysplasia
  — Short trunk and short limbed (Proportionate) – diastrophic dysplasia, mucopolysaccharidoses