Duchenne muscular dystrophy (DMD) is a severe type of muscular dystrophy that primarily affects boys. Muscle weakness usually begins around the age of four, and worsens quickly. Muscle loss typically occurs first in the thighs and pelvis followed by the arms. This can result in trouble standing up. Most are unable to walk by the age of 12. Affected muscles may look larger due to increased fat content. Scoliosis is also common. Some may have intellectual disability. Females with a single copy of the defective gene may show mild symptoms.The disorder is X-linked recessive. About two thirds of cases are inherited from a persons mother, while one third of cases are due to a new mutation. It is caused by a mutation in the gene for the protein dystrophin. Dystrophin is important to maintain the muscle fibers cell membrane. Genetic testing can often make the diagnosis at birth. Those affected also have a high level of creatine kinase in their blood.Although there is no known cure, physical therapy, braces, and corrective surgery may help with some symptoms. Assisted ventilation may be required in those with weakness of breathing muscles. Medications used include steroids to slow muscle degeneration, anticonvulsants to control seizures and some muscle activity, and immunosuppressants to delay damage to dying muscle cells. Gene therapy, as a treatment, is in the early stages of study in humans.
In rare cases, people with DMD have been seen to survive into their forties or early fifties, with proper positioning in wheelchairs and beds, and the use of ventilator support (via tracheostomy or mouthpiece), airway clearance, and heart medications. Early planning of the required supports for later-life care has shown greater longevity for people with DMD.Curiously, in the mdx mouse model of Duchenne muscular dystrophy, the lack of dystrophin is associated with increased calcium levels and skeletal muscle myonecrosis. The intrinsic laryngeal muscles (ILMs) are protected and do not undergo myonecrosis. ILMs have a calcium regulation system profile suggestive of a better ability to handle calcium changes in comparison to other muscles, and this may provide a mechanistic insight for their unique pathophysiological properties. The ILM may facilitate the development of novel strategies for the prevention and treatment of muscle wasting in a variety of clinical scenarios. In addition, patients with Duchenne muscular dystrophy also have elevated plasma lipoprotein levels, implying a primary state of dyslipidemia in patients. Epidemiology
DMD is the most common type of muscular dystrophy; it affects about one in 5,000 males at birth. DMD has an incidence of one in 3,600 male infants.In the US, a 2010 study showed a higher amount of those with DMD age ranging from 5 to 54 who are Hispanic compared to non-Hispanic Whites, and non-Hispanic Blacks. History
The disease was first described by the Neapolitan physician Giovanni Semmola in 1834 and Gaetano Conte in 1836.