Collagen VI related myopathies

Collagen VI related myopathy is a group of muscle diseases that affect skeletal muscles ( the muscles that control movement) and connective tissues ( the body tissues that provides strength and flexibility to the skin, joints and other structures of the body). Most affected persons have muscle weakness and joint deformities called contractures that restrict movement of the affected joints and worsen over time.

Three forms of collagen VI related myopathies have been identified:

• Ullrich congenital muscular dystrophy: the most severe form
• An intermediate form
• Bethlem myopathy : the mildest form

Ullrich congenital muscular dystrophy (UCMD) is the severe form of collagen VI deficiency related myopathy with the following features:

• Babies with UCMD often have hypotonia (low muscle tone or floppiness), and may have reduced movements.
• Sometimes the first signs are only noted after a few months when babies are observed to have poor head control or have a delay in learning new motor skills such as sitting unaided, crawling or walking.
• Children often develop contractures in their neck, hips, knees and elbows, which further restrict movement.
• Rigidity (stiffness) of the spine.
• Some children are never able to walk while others can walk with support. For those who can walk often lose the ability during late childhood or early adolescene.
• Respiratory problems requiring ventilatory support at night.

Bethlem myopathy (BM) is the mild form of collagen VI related myopathy with the following features:

• In childhood, individuals with BM usually have loose joints ( lax joints) and low muscle tone ( hypotonia). They develop contractures during childhood, mainly in their fingers, wrists, elbows, and ankles.
• Muscle weakness can begin at any age betweenchildhood to adulthood. The muscle weakness is slowly progressive, with some affected individuals requiring walking aids during late adulthood.
• Other individuals may have weakness in respiratory muscles, and therefore have breathing problems.
• Skin abnormalities are common. Over the outer surfaces of the arms and legs , small bumps called “follicular hyperkeratosis” could be found. It feels rough or dry to touch.
• Wound healing may also produce scarring in an unusual way, either by forming keloids (raised, rather angry looking scars) or thin shallow silvery “cigarette paper scars”.

Cause

Genetic faults in COL6A1, COL6A2, and COL6A3 genes cause the various forms of collagen VI-related myopathy.

Diagnosis

Complex tests may be needed to work out the causes of collagen VI related myopathies in an affected individual. Muscle biopsy for special immunohistochemical stainings on the collagen VI and a blood sample for DNA testing, are often required. Muscle enzymes (Creatine Kinases) are usually normal.