A new form of severe spondyloepimetaphyseal dysplasia: clinical and radiological characterization.

We report on two patients with a severe form of spondyloepimetaphyseal dysplasia (SEMD). Both patients show normal birth length, early postnatal growth deficiency, severe short stature, flexion contractures in the hips, bowing of the legs with genu varum. Skeletal radiographies show platyspondyly and characteristic vertebral body shape with central indentation of endplates, progressive, and severe metaphyseal changes, very small and irregular proximal femoral epiphyses with severe coxa vara, absence of calcifications, and mild metaphyseal irregularities in upper limbs. The similarities in the skeletal radiographs with SEMD type Strudwick and SEMD matrilin 3 type prompted us to analyze the COL2A1 and MATN3 genes. Direct sequencing of genomic DNA failed to identify any mutation in COL2A1 for both patients and MATN3 sequencing for Patient 1 identified only one heterozygous variant with no predicted damaging effect inherited from an unaffected parent. We therefore conclude that this form of SEMD probably differs from SEMD matrilin 3 type and does not belong to the spectrum of type II collagenopathies. The similarities between our two patients allowed us to propose that they might show a new form of SEMD.