Central core disease

Central core disease is a disorder that affects muscles used for movement (skeletal muscles). This condition causes muscle weakness that ranges from barely noticeable to very severe. The severity of muscle weakness may differ even among affected members of the same family.

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), particularly muscles in the shoulders, upper legs, and hips. Muscle weakness in affected infants can delay the development of motor skills such as sitting, standing, and walking; most people with this condition are able to walk independently. Affected individuals may experience muscle pain (myalgia) or extreme fatigue in response to physical activity (exercise intolerance). Central core disease is also associated with eyes that do not look in the same direction (strabismus), a rounded upper back that also curves to the side (kyphoscoliosis), foot deformities, hip dislocation, and joint deformities called contractures that restrict the movement of certain joints. In severe cases, affected infants experience weakness in the muscles of the face, profound low muscle tone (hypotonia), and serious or life-threatening breathing problems.

Many people with central core disease also have an increased risk of developing a severe reaction to certain drugs used during surgery and other invasive procedures. This reaction is called malignant hyperthermia. Malignant hyperthermia occurs in response to some anesthetic gases, which are used to block the sensation of pain, either given alone or in combination with a muscle relaxant that is used to temporarily paralyze a person during a surgical procedure. If given these drugs, people at risk of malignant hyperthermia may experience a rapid increase in heart rate (tachycardia) and body temperature (hyperthermia), abnormally fast breathing (tachypnea), muscle rigidity, breakdown of muscle fibers (rhabdomyolysis), and increased acid levels in the blood and other tissues (acidosis). The complications of malignant hyperthermia can be life-threatening unless they are treated promptly.

Central core disease gets its name from disorganized areas called central cores, which are typically found in the center of skeletal muscle cells, but can be at the edges or span the length of the cell, in many affected individuals. These abnormal regions can only been seen when muscle tissue is viewed under a microscope. These central cores are often present in cells with few or no mitochondria, which produce energy within cells. Although the presence of central cores can help doctors diagnose central core disease, it is unclear how they are related to muscle weakness and the other features of this condition.