Learn more. The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health. Duchenne and Becker muscular dystrophy. From Genetics Home Reference.
Description Muscular dystrophies are a group of genetic conditions characterized by progressive muscle weakness and wasting atrophy.
Frequency Duchenne and Becker muscular dystrophies together affect 1 in 3, to 5, newborn males worldwide. Inheritance This condition is inherited in an X-linked recessive pattern. Research Studies from ClinicalTrials. Diagnosis and management of Duchenne muscular dystrophy, part 1: diagnosis, and pharmacological and psychosocial management. Lancet Neurol. Epub Nov Pathophysiology of duchenne muscular dystrophy: current hypotheses. Pediatr Neurol. A systematic review and meta-analysis on the epidemiology of Duchenne and Becker muscular dystrophy.
Neuromuscul Disord. Epub Mar Review of Duchenne muscular dystrophy DMD for the pediatricians in the community. Clin Pediatr Phila. Epub Aug Genetics and emerging treatments for Duchenne and Becker muscular dystrophy.
Pediatr Clin North Am. It can begin as early as age 2 or 3, first affecting the proximal muscles those close to the core of the body and later affecting the distal limb muscles those close to the extremities. Usually, the lower external muscles are affected before the upper external muscles. The affected child might have difficulty jumping, running, and walking. Other symptoms include enlargement of the calves, a waddling gait, and lumbar lordosis an inward curve of the spine.
Later on, the heart and respiratory muscles are affected as well. Progressive weakness and scoliosis result in impaired pulmonary function, which can eventually cause acute respiratory failure.
DMD was first described by the French neurologist Guillaume Benjamin Amand Duchenne in the s, but until the s, little was known about the cause of any kind of muscular dystrophy.
In , the protein associated with this gene was identified and named dystrophin. Lack of the dystrophin protein in muscle cells causes them to be fragile and easily damaged. DMD has an X-linked recessive inheritance pattern and is passed on by the mother, who is referred to as a carrier.
DMD carriers are females who have a normal dystrophin gene on one X chromosome and an abnormal dystrophin gene on the other X chromosome. Most carriers of DMD do not themselves have signs and symptoms of the disease, but a minority do. Symptoms can range from mild skeletal muscle weakness or cardiac involvement to severe weakness or cardiac effects and can begin in childhood or adulthood. Until relatively recently, boys with DMD usually did not survive much beyond their teen years. It is caused by an alteration mutation in a gene, called the DMD gene that can be inherited in families in an X-linked recessive fashion, but it often occurs in people from families without a known family history of the condition.
Individuals who have DMD have progressive loss of muscle function and weakness, which begins in the lower limbs. The DMD gene is the second largest gene to date, which encodes the muscle protein, dystrophin. Boys with Duchenne muscular dystrophy do not make the dystrophin protein in their muscles. Duchenne muscular dystrophy affects approximately 1 in male births worldwide.
Because this is an inherited disorder, risks include a family history of Duchenne muscular dystrophy. The symptoms usually appear before age 6 and may appear as early as infancy.
Typically, the first noticeable symptom is delay of motor milestones, including sitting and standing independently. The mean age for walking in boys with Duchenne muscular dystrophy is 18 months.
There is progressive muscle weakness of the legs and pelvic muscles, which is associated with a loss of muscle mass wasting. This muscle weakness causes a waddling gait and difficulty climbing stairs. Muscle weakness also occurs in the arms, neck, and other areas, but not as severely or as early as in the lower half of the body. Calf muscles initially enlarge and the enlarged muscle tissue is eventually replaced with fat and connective tissue pseudohypertrophy. Muscle contractures occur in the legs, making the muscles unusable because the muscle fibers shorten and fibrosis occurs in connective tissue.
Occasionally, there can be pain in the calves. Symptoms usually appear in boys aged 1 to 6. There is a steady decline in muscle strength between the ages of 6 and 11 years.
By age 10, braces may be required for walking, and by age 12, most boys are confined to a wheelchair. Bones develop abnormally, causing skeletal deformities of the spine and other areas. Muscular weakness and skeletal deformities frequently contribute to breathing disorders. Cardiomyopathy enlarged heart occurs in almost all cases, beginning in the early teens in some, and in all after the age of 18 years. Intellectual impairment may occur, but it is not inevitable and does not worsen as the disorder progresses.
Few individuals with DMD live beyond their 30s. Breathing complications and cardiomyopathy are common causes of death. Duchenne muscular dystrophy is diagnosed in several ways. A clinical diagnosis may be made when a boy has progressive symmetrical muscle weakness. The symptoms present before age 5 years, and they often have extremely elevated creatine kinase blood levels which are described below.
0コメント