Bethlem Myopathy

Bethlem myopathy may also be referred to as a collagen type VI-related disorder. In Bethlem myopathy, collagen VI is not working properly, due to a genetic variant in one of the genes that code for collagen VI: COL6A1, COL6A2, or COL6A3.

When Bethlem myopathy was first described, it was referred to as benign myopathy with autosomal dominant inheritance. Other older terms that have been used are benign congenital myopathy, benign congenital myopathy muscular dystrophy, and benign congenital myopathy with contractures.

Bethlem myopathy is a rare condition. As of January 2019, it is estimated to affect less than 1 in 1,000,000 people. The condition is variable and can have mild symptoms, so it is believed that Bethlem myopathy is like underdiagnosed, which means that some people who have Bethlem myopathy have not been diagnosed with Bethlem myopathy.

The healthy problems associated with Bethlem myopathy are proximal muscle weakness and contractures. Proximal muscle weakness is weakness of the muscles closer to the torso. The muscle weakness becomes slowly worse over time. Contractures are joint stiffness that results in limited mobility of the joints. The joints typically cannot be completely straightened actively or passively. The contractures may come and go.

Bethlem myopathy is considered a muscular dystrophy. Muscular dystrophies are a group of disorders that cause muscle weakness and loss of muscle mass because the proteins that make up the muscles are not formed properly. These symptoms become worse over time.