A qualitative or quantitative defect of collagen 6 disorder that covers a wide spectrum of musculoskeletal phenotypes caused by dominant and recessive mutations in the three major collagen VI genes: COL6A1, COL6A2, and COL6A3. These variants lead to a variety of overlapping phenotypes, ranging from severe congenital muscle weakness, hypotonia, torticollis and contractures with loss or non-development of ambulation on one end and childhood to adult onset mild muscle weakness, stiffness, and joint hyperlaxity on the other.