Bethlem myopathy falls under the category of congenital muscular dystrophies, within a sub-type known as the ‘collagen VI-related myopathies’.
Bethlem myopathy has the following specific features:
- the joints of the hands develop ‘contractures’ or ‘tightness’ at the level of the fingers, and the feet develop ‘contractures’ or ‘tightness’ of the Achilles tendons
- a variable degree of muscle weakness, affecting the legs especially and to a lesser extent the arms, develops and slowly progresses over time
- respiratory muscles are more mildly affected, and problems related to respiratory insufficiency are very rare and limited to the late adult years.