COL1-related overlap disorder: A novel connective tissue disorder incorporating the osteogenesis imperfecta/Ehlers-Danlos syndrome overlap

Silvia Morlino, Lucia Micale, Marco Ritelli, Marianne Rohrbach, Nicoletta Zoppi, Anthony Vandersteen, Sara Mackay, Emanuele Agolini, Dario Cocciadiferro, Erina Sasaki, Annalisa Madeo, Alessandro Ferraris, Willie Reardon, Maja Di Rocco, Antonio Novelli, Paola Grammatico, Fransiska Malfait, Tommaso Mazza, Alan Hakim, Cecilia GiuntaMarina Colombi, Marco Castori

Research output: Contribution to journalArticle


The 2017 classification of Ehlers-Danlos syndromes (EDS) identifies three types associated with causative variants in COL1A1/COL1A2 and distinct from osteogenesis imperfecta (OI). Previously, patients have been described with variable features of both disorders, and causative variants in COL1A1/COL1A2; but this phenotype has not been included in the current classification. Here, we expand and re-define this OI/EDS overlap as a missing EDS type. Twenty-one individuals from 13 families were reported, in whom COL1A1/COL1A2 variants were found after a suspicion of EDS. None of them could be classified as affected by OI or by any of the three recognized EDS variants associated with COL1A1/COL1A2. This phenotype is dominated by EDS-related features. OI-related features were limited to mildly reduced bone mass, occasional fractures and short stature. Eight COL1A1/COL1A2 variants were novel and five recurrent with a predominance of glycine substitutions affecting residues within the procollagen N-proteinase cleavage site of α1(I) and α2(I) procollagens. Selected variants were investigated by biochemical, ultrastructural and immunofluorescence studies. The pattern of observed changes in the dermis and in vitro for selected variants was more typical of EDS rather than OI. Our findings indicate the existence of a wider recognizable spectrum associated with COL1A1/COL1A2.
Original languageEnglish
JournalClin. Genet.
Publication statusPublished - Jan 1 2019



  • COL1A1
  • COL1A2
  • Ehlers-Danlos syndrome
  • joint hypermobility
  • osteogenesis imperfecta

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