Which critical orthopaedic complication is highly characteristic of Morquio syndrome (Mucopolysaccharidosis Type IV) and requires vigilant clinical monitoring?

Explanation:
Morquio syndrome is a lysosomal storage disease leading to severe skeletal dysplasias (dysostosis multiplex). A hallmark and potentially lethal complication is atlantoaxial instability, which is caused by a combination of odontoid hypoplasia and severe ligamentous laxity. If left untreated, it can rapidly progress to cervical myelopathy and death. Reference: Tachdjian's Pediatric Orthopaedics, 6th Edition.