Heritable connective tissue disease: A disorder due to mutation of a gene responsible for connective tissue, the material that gives tissues form and strength. These mutations may change the structure and development of skin, bones, joints, heart, blood vessels, lungs, eyes, and ears. Some mutations also change how these tissues work. There are over 300 mutations affecting collagen, a protein found in skin, bone, cartilage, and all other connective tissues. Examples of heritable connective tissue disease include such conditions as Marfan syndrome, osteogenesis imperfecta, epidermolysis bullosa, Ehlers-Danlos syndrome.