From MedlinePlus Genetics
Collagen VI-related dystrophy 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 dystrophy, which range in severity: Bethlem muscular dystrophy is the mildest, an intermediate form is moderate in severity, and Ullrich congenital muscular dystrophy is the most severe.

People with Bethlem muscular dystrophy usually have low muscle tone (hypotonia) in infancy. 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, particularly when outdoors. Affected individuals usually develop contractures by adulthood, typically in their fingers, elbows, shoulders, and ankles. Older individuals may develop weakness in respiratory muscles, which can cause breathing problems. Some people with this mild form of collagen VI-related dystrophy 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 dystrophy 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 their fingers, elbows, shoulders, and ankles 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 early adolescence. Individuals with Ullrich congenital muscular dystrophy develop contractures in their shoulders, elbows, hips, and knees, which further impair movement. Many individuals with this form of the condition have loose joints (joint laxity) in the fingers, wrists, toes, ankles, and other joints. Affected individuals need continuous mechanical ventilation to help them breathe while sleeping, and some may need it in the daytime. As in Bethlem muscular dystrophy, 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 dystrophy 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.  https://medlineplus.gov/genetics/condition/collagen-vi-related-myopathy