Central core disease (CCD) is a form of muscular dystrophy. It falls under the category of congenital myopathies (which means it’s an inherited condition), in which type 1 skeletal muscle fibers exhibit amorphous area -cores’ that lack mitochondria and oxidative enzyme activity that run the length of the myofibre. Central core disease is also known as:
- Central core myopathy
- Shy-Magee syndrome (after the people who originally researched it in 1956)
- CCD or CCO
- Muscle core disease
- Myopathy, Central Fibrillar
Most people with central core disease experience persistent, mild muscle weakness that does not worsen with time. This weakness affects the muscles near the center of the body (proximal muscles), particular muscles in the upper legs and hips. Muscle weakness causes affected infants to appear “floppy” and can delay the development of motor skills such as sitting, standing, and walking. In severe cases, affected infants experience profoundly weak muscle tone (hypotonia) and serious or life-threatening breathing problems. Central core disease is also associated with skeletal abnormalities such as abnormal curvature of the spine (scoliosis), hip dislocation, and joint deformities called contractures that restrict the movement of certain joints. Some individuals with CCD have an increased chance of having a severe reaction to anesthesia, called malignant hyperthermia, which may cause muscle rigidity or breakdown (rhabdomyolysis), a high fever, or a rapid heartbeat. The complications of malignant hyperthermia can be life-threatening unless they are treated promptly.
Central core disease is usually inherited in an autosomal dominant way (however there have been some rare cases resulting from autosomal recessive inheritance). It is a result of an alteration in the RYR1 gene located on the long arm (q) of chromosome 19 (19q13.1) RYR1 provides instructions for making a protein called ryanodine receptor 1 that allows muscles to contract normally. When this protein is altered as a result of the mutation, muscles do not mature normally or contract normally and start to weaken.
Central core disease affects males and females in equal numbers. The exact incidence and prevalence of CCD are unknown. CCD is believed to be the most common form of congenital myopathy, which as a group occurs in 6 out of every 100,000 live births.
A number of examinations need to be performed to diagnose Central Core Disease, these include: a physical examination to identify muscle weakness, family history, a muscle biopsy that reveals a characteristic appearance of the muscle cells, blood tests to measure levels of enzyme creatine kinase, electromyography (EMG), nerve conduction velocity studies and also genetic testing that identifies a mutation in the RYR1. The prenatal diagnosis such as amniocentesis and chorionic villus sampling is available for families where the mutation has been identified as being in the RYR1 gene.
No curative treatment is currently available for CCD and management is essentially supportive based on a multidisciplinary approach. Physiotherapy is recommended to increase or maintain muscle function and mobility. It also helps to delay the onset of curvature of the spine (scoliosis) and help prevent the development of contractures. Moderate exercise such as swimming, walking or pedaling may help maintain a healthy cardiovascular system and a steady weight. It is important to monitor for lung function as breathing may be affected by muscle weakness. Breathing exercises or other breathing support treatments may be beneficial. Corrective surgery may be performed for scoliosis. In young children, a spinal brace may be used and in children who do not walk, molded seating is used.
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