Etiology:

• Dysfunction in laying down of collagen – endochondral plates in limbs not well ossified
• AD – Replacement of ARG for GLY in gene coding FGFR3
• Therefore constant activation of FGF
• Therefore interference with endochondral ossification at epiphyseal growth plates of long bones

Thanatophoric dwarfism – Missense/ point mutation in FGFR3. Fatal

Clinical:

• Long bones abnormally short
• Skull – normal growth, trunk normal growth
• Lordosis
• Long trunk
• Protrusive mandible – malocclusion

Histology:

• Disorganized & narrow zones of proliferation & hypertrophy
• Enlarged chondrolytes