Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a dystrophinopathy, and is the most common muscular dystrophy. DMD is estimated to affect 1/3300 male births, while the condition is extremely rare in females, due to its pattern of inheritance, as we will see below.

This neuromuscular disease is characterized by: progressive muscle weakness; from a degeneration of skeletal, smooth and cardiac muscles that begins in early childhood.

Typically the proximal muscles of the lower limb and trunk are affected first. Eventually there is a progression to the muscles and extremities of the upper extremities.

In addition to motor weakness and delayed motor development milestones or global retardation, patients also show muscle pseudohypertrophy, especially of the calves, a swaying gait, scoliosis, joint contractures, and Gower’s classic but non-specific sign of proximal muscle weakness. Typically, children become wheelchair bound around 12 years of age 1.

In addition, patients suffering from Duchenne muscular dystrophy have many other non-musculoskeletal features:

  • dilated cardiomyopathy leading to congestive heart failure;
  • electrocardiographic abnormalities, such as interventricular conduction delay with enlargement of the QRS complex (duration >0.12 seconds), narrow Q waves (<0.04s), deep in the lateral and high lateral precordial leads, prominent R waves in V1 (R/S >1)
  • Restrictive ventilatory defect
  • mental disability

Duchenne muscular dystrophy is inherited with an X-linked recessive pattern and therefore occurs almost exclusively in males.

It is due to a mutation in the DMD gene that normally codes for dystrophin, a protein involved in strengthening skeletal and cardiac muscle fibers by acting as a mechanical link between the cytoskeleton and the extracellular glycoprotein matrix of the cells of these tissues.

Unlike Becker muscular dystrophy, where a mutation in the DMD gene results in a partially functioning dystrophin protein, in Duchenne muscular dystrophy the protein does not work, which results in a more severe phenotype.


The diagnosis of Duchenne muscular dystrophy is based on:

  1. on the observation of signs and symptoms
  2. on clinical observation and laboratory tests that highlight muscle damage. In particular, an important value is that of creatine kinase, an enzyme that is released into the bloodstream when there is muscle damage.
  3. on molecular analysis of the dystrophin gene and, if necessary, through muscle biopsy (to verify the amount of dystrophin present in the muscle).
  4. on family history analysis
  5. on the results of an electromyography, a diagnostic procedure aimed at assessing the state of health of the muscles and peripheral nerves that control their activity.

In a situation at risk, or in the case of a woman who knows she is a healthy carrier of dystrophinopathy, prenatal diagnosis can be made by chorionic villus sampling or amniocentesis.

Treatment and prognosis

Corticosteroids are effective in improving muscle strength and respiratory function 1 and are the mainstay of treatment.

In contrast, the management of DMD is multidisciplinary and involves rehabilitation and surveillance of respiratory, cardiac and orthopedic complications. Many patients require a heart transplant to prolong survival.

The prognosis remains relatively poor, with most patients not surviving beyond the third decade of life.

Katherine Johnson, M.D., is a board-certified obstetrician-gynecologist with clinical expertise in general obstetrics and gynecology, family planning, women’s health, and gynecology.

She is affiliated with the Obstetrics and Gynecology division at an undisclosed healthcare institution and the online platform, Maternicity.com.

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