What are the genetic changes related to hereditary myopathy with early respiratory failure ?
HMERF can be caused by a mutation in the TTN gene. This gene provides instructions for making a protein called titin. Titin plays an important role in muscles the body uses for movement (skeletal muscles) and in heart (cardiac) muscle.  Within muscle cells, titin is an essential component of structures called sarcomeres. Sarcomeres are the basic units of muscle contraction; they are made of proteins that generate the mechanical force needed for muscles to contract. Titin has several functions within sarcomeres. One of its most important jobs is to provide structure, flexibility, and stability to these cell structures. Titin also plays a role in chemical signaling and in assembling new sarcomeres.  The TTN gene mutation responsible for HMERF leads to the production of an altered version of the titin protein. Studies suggest that this change may disrupt titin's interactions with other proteins within sarcomeres and interfere with the protein's role in chemical signaling. Consequently, muscle fibers become damaged and weaken over time. It is unclear why these effects are usually limited to proximal muscles and muscles involved in breathing.  Some people with the characteristic features of HMERF do not have identified mutations in the TTN gene. In these cases, the genetic cause of the condition is unknown.