Compound phenotype of osteogenesis imperfecta and Ehlers–Danlos syndrome caused by combined mutations in COL1A1 and COL5A1

Osteogenesis imperfecta (OI) is an inherited connective tissue disorder with a broad clinical spectrum that can overlap with Ehlers–Danlos syndrome (EDS). To date, patients with both OI and EDS have rarely been reported. In the present study, we investigated a family with four members, one healthy individual, one displaying OI only, and two displaying the compound phenotype of OI and EDS, and identified the pathogenic mutations. Whole exome sequencing was applied to the proband and her brother. To verify that the mutations were responsible for the pathogenesis, conventional Sanger sequencing was performed for all members of the family. We identified a known COL1A1 (encoding collagen type I α 1 chain) mutation (c.2010delT, p.Gly671Alafs*95) in all three patients (the proband, her brother, and her mother) in this family, but also a novel heterozygous COL5A1 (encoding collagen type V α 1 chain) mutation (c.5335A>G, p.N1779D) in the region encoding the C-terminal propeptide domain in the proband and her mother, who both had the compound phenotype of OI and EDS. The results of the present study suggested that the proband and her mother presented with the compound OI–EDS phenotype caused by pathogenic mutations in COL5A1 and COL1A1.