What is (are) collagen VI-related myopathy ?
Collagen VI-related myopathy is a group of disorders that affect skeletal muscles (which are the muscles used for movement) and connective tissue (which provides strength and flexibility to the skin, joints, and other structures throughout the body). Most affected individuals have muscle weakness and joint deformities called contractures that restrict movement of the affected joints and worsen over time. Researchers have described several forms of collagen VI-related myopathy, which range in severity: Bethlem myopathy is the mildest, an intermediate form is moderate in severity, and Ullrich congenital muscular dystrophy is the most severe.  People with Bethlem myopathy usually have loose joints (joint laxity) and weak muscle tone (hypotonia) in infancy, but they develop contractures during childhood, typically in their fingers, wrists, elbows, and ankles. Muscle weakness can begin at any age but often appears in childhood to early adulthood. The muscle weakness is slowly progressive, with about two-thirds of affected individuals over age 50 needing walking assistance. Older individuals may develop weakness in respiratory muscles, which can cause breathing problems. Some people with this mild form of collagen VI-related myopathy have skin abnormalities, including small bumps called follicular hyperkeratosis on the arms and legs; soft, velvety skin on the palms of the hands and soles of the feet; and abnormal wound healing that creates shallow scars.  The intermediate form of collagen VI-related myopathy is characterized by muscle weakness that begins in infancy. Affected children are able to walk, although walking becomes increasingly difficult starting in early adulthood. They develop contractures in the ankles, elbows, knees, and spine in childhood. In some affected people, the respiratory muscles are weakened, requiring people to use a machine to help them breathe (mechanical ventilation), particularly during sleep.  People with Ullrich congenital muscular dystrophy have severe muscle weakness beginning soon after birth. Some affected individuals are never able to walk and others can walk only with support. Those who can walk often lose the ability, usually in adolescence. Individuals with Ullrich congenital muscular dystrophy develop contractures in their neck, hips, and knees, which further impair movement. There may be joint laxity in the fingers, wrists, toes, ankles, and other joints. Some affected individuals need continuous mechanical ventilation to help them breathe. As in Bethlem myopathy, some people with Ullrich congenital muscular dystrophy have follicular hyperkeratosis; soft, velvety skin on the palms and soles; and abnormal wound healing.  Individuals with collagen VI-related myopathy often have signs and symptoms of multiple forms of this condition, so it can be difficult to assign a specific diagnosis. The overlap in disease features, in addition to their common cause, is why these once separate conditions are now considered part of the same disease spectrum.