Congenital Myopathies

Central core myopathy and multiminicore myopathy are the most common form of congenital myopathy.

Most newborns have severely reduced muscle tone (hypotonia, or "floppiness") and mild muscle weakness Weakness Weakness refers to loss of muscle strength. That is, people cannot move a muscle normally despite trying as hard as they can. However, the term is often misused. Many people with normal muscle... read more , but sometimes symptoms of core myopathy do not manifest until adulthood. Many people also have facial weakness. The weakness does not become worse, and life expectancy is normal, but some people are severely affected and require a wheelchair. People who have central core myopathy are at increased risk of a life-threatening disorder of elevated body temperature called malignant hyperthermia Malignant Hyperthermia Malignant hyperthermia is a rare, life-threatening rise in body temperature that occurs in susceptible people who are given certain muscle-relaxing drugs plus an anesthetic gas for surgery.... read more .

Centronuclear myopathies are inherited in various ways. The forms that are inherited via a gene carried on the X chromosome (see X-Linked Inheritance X-Linked Inheritance Genes are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body. Chromosomes are made of a very long strand... read more ) are the most common and most severe, and most affected children do not survive beyond the first year of life. Symptoms of the autosomal dominant Dominant disorders Genes are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body. Chromosomes are made of a very long strand... read more forms typically appear in adolescence or adulthood. People who have one of these forms have muscle pain caused by exercise, facial weakness, droopy eyelids, and weakness of the eye muscles.

Nemaline myopathy, one of the more common congenital myopathies, can be autosomal dominant or autosomal recessive Recessive disorders Genes are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body. Chromosomes are made of a very long strand... read more .

Nemaline myopathy may be severe, moderate, or mild. People who have a severe form may have weakness of the muscles used for breathing and respiratory failure Respiratory Failure Respiratory failure is a condition in which the level of oxygen in the blood becomes dangerously low or the level of carbon dioxide in the blood becomes dangerously high. Conditions that block... read more . People who have a moderate form may have weakness in muscles of the face, neck, trunk, and feet that becomes worse over time, but their life expectancy may be nearly normal. People who have a mild form have weakness that does not worsen, and their life expectancy is normal.