Achondroplasia is the most common form of short-limbed dwarfism. It is caused by an constitutive activation of fibroblast growth factor receptor 3 (FGFR3), which results in inhibition of chondrocyte proliferation. This leads to the failure of longitudinal bone growth (endochondral ossification) and short limbs.  Membranous ossification is not affected, which results in a large head relative to limbs.  This dysplasia is characterized by midface hypoplasia, macrocephaly and rhizomelia (short arms and legs, preferentially involving the proximal limb segments).  More than 85% of mutations occur sporadically. It is an autosomal dominant disorder with full penetrance (homozygosity is lethal).  Complications include craniocervical junction compression, spinal stenosis, sleep apnea, and frequent ear infections in pediatric population. 

This case was submitted with supervision and input from:

Soni C. Chawla, M.D.
Associate Professor
Department of Radiological Sciences
David Geffen School of Medicine at UCLA
Olive View - UCLA Medical Center