Reza Mollahouseini, Abolfazl Rahimizadeh, Walter Wiliamson
Background: Achondroplasia is a rare genetic disorder affecting bone development, resulting in disproportionate short stature. The coexistence of os odontoideum (OO) in individuals with achondroplasia is exceptionally uncommon. Case Description: We present the case of a 29-year-old female with achondroplasia who experienced progressive weakness in the extremities, ultimately leading to difficulty in ambulation. Radiographic evaluation revealed an atlantoaxial dislocation secondary to an unstable OO. Surgical stabilization of C1-C2 resulted in gradual yet significant neurological recovery. Conclusion: Since the first reported case in 1974, only a limited number of achondroplastic individuals with atlantoaxial dislocation due to OO have been documented.