Myosin storage myopathy (Myosin storage myopathy) - Gen MYH7.

The storage myopathy myosin is an alteration causing a myopathy not worsening, or worsens very slowly over time. This alteration is characterized by clumping of proteins containing a protein called myosin, within certain muscle fibers. Usually the signs and symptoms of myosin storage myopathy become evident in childhood, but may manifest themselves later. Because muscle weakness, affected individuals may start walking later than usual and have a waddling gait, trouble climbing stairs, and difficulty raising your arms above shoulder height. Muscle weakness also causes some affected individuals have trouble breathing.

This process is due to mutations in MYH7, located on the long arm of chromosome 14 (14q12). This gene encodes a protein called myosin beta (?) cardiac heavy chain, located in the heart muscle and type I skeletal muscle fibers. This protein is the main component of the thick filament in sarcomeres. Sarcomeres, which are composed of thick and thin filaments, are the basic units of muscle contraction.

They have identified at least five mutations in MYH7 that are involved in the storage myopathy myosin. Mutations in MYH7 lead to coding a beta myosin (?) cardiac heavy chain, which is believed to be less capable of forming thick filaments. The altered proteins accumulate in skeletal muscle fibers of type I, forming groups of proteins characteristic of the disease. It is unclear how these changes lead to muscle weakness in people with myosin storage myopathy.

The storage myopathy myosin is inherited as an autosomal dominant, which means that a copy of the altered gene in each cell is sufficient to express the disease. In some cases, an affected person inherits the mutation from an affected parent. Other cases are due to new mutations in the gene and occur in people with no history of disease in your family.

Tests in IVAMI: in IVAMI perform detection of mutations associated with myosin storage myopathy, by complete PCR amplification of exons MYH7, and subsequent sequencing.

Samples recommended: EDTA blood collected for separation of blood leukocytes, or impregnated sample card with dried blood (IVAMI may mail the card to deposit the blood sample).