Rigid spine muscular dystrophy (RSMD) – SELENON (SEPN1) gene

Rigid spinal muscular dystrophy (RSMD), also known as congenital muscular dystrophy with rigid spine syndrome, belongs to a group of disorders characterized by muscle weakness and atrophy. In particular, RSMD causes weakness of the axial muscles, stiffness of the spine and severe respiratory problems.

The signs of this process are usually evident at birth or in the first months of life. Affected newborns may suffer from hypotonia, and later the muscles surrounding the spine and spinal joints develop contractures that restrict movement. Other signs and symptoms related to this process may include scoliosis, atrophy of the muscles in the inner thighs and respiratory failure.

This process is due in 40 percent of cases to mutations in the SELENON gene (selenoprotein N), located on the short arm of chromosome 1 (1p36.11). In the rest of the cases the genetic cause that leads to the development of the disease is unknown.

The SELENON gene encodes the protein called selenoprotein N. Although the exact function of selenoprotein N is unknown, it is likely to be involved in the protection of cells against oxidative stress. It is believed that this protein plays a role in myogenesis and muscle function after birth. This protein contains a region that probably allows it to interact with calcium. More than a dozen mutations in the SELENON gene have been described in individuals with rigid spinal muscular dystrophy. It is believed that the identified mutations reduce the amount of selenoprotein N or affect its activity in the cells. However, it is not clear how a functional selenoprotein N deficiency affects tissue formation or muscle function.

This disease is inherited with an autosomal recessive pattern, which means that both copies of the gene in each cell must have mutations for the alteration to be expressed. The parents of an individual with an autosomal recessive disease have a copy of the mutated gene, but usually do not show signs and symptoms of the disease.

Tests performed in IVAMI: in IVAMI we perform the detection of mutations associated with the rigid spinal muscular dystrophy (RSMD), by means of the complete PCR amplification of the exons of the SELENON gene, and their subsequent sequencing.

Recommended samples: non-coagulated blood obtained with EDTA for separation of blood leucocytes, or a card with a dried blood sample (IVAMI can mail the card to deposit the blood sample).