Distinctive tomographic features of atlantoaxial dislocation have been encountered in a child with du Pan syndrome. Three-dimensional computed tomography scan showed agenesis of the odontoid process associated with significant hypoplasia of the left lateral mass of the odontoid. Bidirectional fluorescent DNA sequencing have been used to identify mutations in the complete coding region (exon 1-2) of the cartilage-derived morphogenic protein 1 gene. No mutation was detected in the analysed region. We report what might be a novel variant of acromesomelic du Pan syndrome.