Common symptoms related to muscle weakness include weakness of the eye muscles (opthalmoparesis) and generalized muscle weakness, typically affecting the muscles closest to the torso of the body (proximal muscle weakness).
This weakness affects the muscles near the center of the body (proximal muscles), particularly muscles in the upper legs and hips.
Muscle weakness can also cause affected infants to appear “floppy” and can delay the development of motor skills such as sitting, standing, and walking.
Breathing problems associated with RYR-1-related diseases can range from non-existent to severe and are due to weakness in the muscles of the chest wall.
Mild breathing problems can include sleep apnea, requiring breathing support during sleep (CPAP/Bi PAP).
A mutation in the gene can alter the number, structure, and/or function of the RYR-1 receptor, which can lead to a wide range of symptoms, as detailed above.
There are many different mutations that can occur in the RYR-1 gene which have differing clinical consequences.
A reduced number and/or abnormal RYR-1 receptors can lead to dysfunctional muscle contraction, weakness, susceptibility to malignant hyperthermia, rhabdomyolysis, as well as other exercise- and/or heat-induced symptoms.
There is a wide range of symptoms for RYR-1-related muscle weakness, but they are typically either non-progressive or very slowly progressive.
The prevalence is approximately 1/90,000 in the United States.
The disorder most likely goes misdiagnosed or undiagnosed making it difficult to determine the true frequency in the general population.
mutations are typically associated with core myopathies and are the most common overall cause of congenital myopathy.