Characteristic findings of achondroplasia include rhizomelic limb shortening, normal intelligence, frontal bossing, and spinal stenosis. Cervical spine instability is not prevalent in achondroplasia, but is is present in pseudoachondroplasia, a skeletal dysplasia due to cartilage oligometric matrix protein (COMP) gene.
Achondroplasia, caused by a defective FGFR3 affecting the proliferative zone of the physis, is characterized by rhizomelic shortening of the extremities. Rhizomelic shortening is defined as disproportionate shortening of the proximal segment of limbs, and is characteristically found in achondroplastic patients. Inheritance is typically autosomal dominant, although spontaneous mutations are not uncommon. Characteristic findings include frontal bossing, trident hands, thoracolumbar kyphosis, shortened pedicles causing spinal stenosis, genu varum, muscular hypotonia, and normal intelligence.
Shirley et al report achondroplasia, the most common skeletal dysplasia, is caused by a mutation of fibroblast growth factor receptor-3. This disorder is characterized by frontal bossing, midface hypoplasia, otolaryngeal system dysfunction, and rhizomelic short stature."
Illustration A is a clinical example of achondroplasia. Illustration B demonstrates the difference between different forms of dwarfism.
Shirley ED, Ain MC. Achondroplasia: manifestations and treatment. J Am Acad Orthop Surg. 2009 Apr;17(4):231-41. Review. PubMed PMID: 19307672.
PMID:19307672 (Link to Abstract)