COL2A1 and spondyloepiphyseal dysplasia congenita: However, definitive correlations between genotype and phenotype in the COL2A1 C-propeptide mutation and atypical SEDC currently remain unclear, and it is inconclusive whether 2 cases reported by Tarhal et al.7 with COL2A1 C-propeptide mutations had delayed pubic bone ossification.