About RYR-1 Muscle Disease
Overview: The term "congenital myopathy" refers to a group of muscle conditions with muscle weakness beginning at birth or in early childhood. Mutations or changes in the RYR-1 gene are the most common cause of congenital muscle weakness (myopathy). The RYR-1 receptor is a channel in muscle cells that regulates the flow of calcium, a critical component of muscle contraction. A reduced number and/or abnormal RYR-1 channels lead to dysfunctional muscle contraction and weakness. There is a wide range of symptoms for RYR-1 myopathy, but are typically either non-progressive or very slowly progressive.
Symptoms: Common symptoms include weakness of the eye muscles and generalized muscle weakness, typically affecting the muscles closest to the torso of the body. Some individuals experience muscle cramping and pain, difficulties exercising, and intolerance to heat. There are typically no heart problems and intelligence is not affected.
Breathing Problems: Breathing problems associated with RYR-1 myopathy 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 (stop breathing while asleep), requiring breathing support during sleep. Severe breathing problems require continuous support.
Malignant Hyperthermia: Changes in the RYR-1 gene have also been associated with malignant hyperthermia, a severe and potentially fatal reaction to certain types of anesthesia (drugs given by a doctor for a medical/surgical procedure). Anyone with an RYR-1 genetic abnormality should take "malignant hyperthermia precautions" if anesthesia is required for a medical/surgical procedure. Please click here for a guide for patients at risk for malignant hyperthermia.
Diagnosis: RYR-1 myopathy is diagnosed with genetic testing. In addition, a muscle biopsy can be performed, which allows doctors to examine the muscle under the microscope and look for changes at a cellular level that may be associated with the RYR-1 myopathy. MRI also allows the doctors to look for characteristic changes in the muscle at a structural level.
How does someone get RYR-1 muscle disease? RYR-1 myopathy is due to a change or mutation in the RYR-1 gene. This mutation in the RYR-1 gene is usually inherited from one or both parents, who may or may not be affected by the disease. There are two types of inheritance patterns for changes in this gene: autosomal dominant and autosomal recessive. "Recessive" means that both "copies" of the gene must have mutations for the patient to be affected; if only one copy is defective, the patient will be a carrier and not be affected clinically (signs & symptoms). "Dominant" means that even if only one copy of the gene is defect, the patient will be affected by the disease.
Treatment: At this time, no cure exists for RYR-1 myopathy. The goal of this Foundation is to help find one.