Duchenne muscular dystrophy

Duchenne muscular dystrophy
Dr. Edwin P. Ewing, Jr. · Public domain · source
Name	Duchenne muscular dystrophy
Symptoms	Progressive muscle weakness, delayed motor milestones, cardiomyopathy, respiratory failure
Onset	Childhood
Causes	Mutation in dystrophin gene (X-linked recessive)
Diagnosis	Genetic testing, elevated creatine kinase, muscle biopsy
Treatment	Corticosteroids, exon-skipping therapies, gene therapy, supportive care
Prognosis	Reduced life expectancy without intervention

Duchenne muscular dystrophy is a genetic neuromuscular disorder characterized by progressive skeletal muscle degeneration and weakness beginning in early childhood, most commonly affecting boys. It results from loss of functional dystrophin protein, leading to myofiber fragility, chronic inflammation, and replacement of muscle by fibrofatty tissue. Care involves multidisciplinary teams combining pharmacologic, rehabilitative, and surgical approaches to address motor decline, cardiopulmonary complications, and quality of life.

Signs and symptoms

Early motor delays and proximal muscle weakness manifest as delayed walking, frequent falls, and difficulty rising, often producing a positive Gowers' sign; clinicians may observe calf pseudohypertrophy and lumbar lordosis. Progressive loss of ambulation typically occurs in adolescence, accompanied by scoliosis and contractures that may require orthopedic interventions; cardiomyopathy, arrhythmias, and dilated cardiomyopathy emerge with age, and respiratory insufficiency leads to hypoventilation and recurrent infections. Neurocognitive and behavioral features such as learning disability and attention deficits are reported, and endocrine consequences including delayed puberty and osteoporosis may complicate long-term care.

Genetics and pathophysiology

The disorder is caused by mutations in the dystrophin gene located on the X chromosome, leading to absence or severe reduction of dystrophin, a cytoskeletal protein that links the sarcolemma to the extracellular matrix. Loss of dystrophin disrupts the dystrophin-associated protein complex, increasing sarcolemmal permeability, calcium influx, and activation of proteases and inflammatory cascades, which culminate in myonecrosis and replacement with fibrofatty tissue. Molecular mechanisms considered in therapeutic development include nonsense mutations amenable to read-through compounds, frame-shifting deletions targeted by exon-skipping antisense oligonucleotides, and gene-replacement strategies using viral vectors to deliver micro- or mini-dystrophin constructs.

Diagnosis

Clinical evaluation integrates family history, pattern of weakness, and characteristic signs with laboratory testing such as markedly elevated serum creatine kinase levels. Definitive diagnosis is achieved through genetic testing including multiplex ligation-dependent probe amplification, next-generation sequencing panels, and deletion/duplication analysis of the dystrophin gene; muscle biopsy with immunohistochemistry or Western blot for dystrophin may be used when genetic results are inconclusive. Cardiac assessment with echocardiography and cardiac MRI, pulmonary function testing including spirometry and overnight oximetry, and neurodevelopmental evaluation inform baseline status and surveillance planning.

Management and treatment

Management is multidisciplinary, involving neurologists, cardiologists, pulmonologists, orthopedists, physiotherapists, and genetic counselors to implement individualized care plans. Corticosteroids such as prednisone and deflazacort slow loss of ambulation and preserve pulmonary and cardiac function; cardiac failure is managed with angiotensin-converting enzyme inhibitors, beta-blockers, and aldosterone antagonists when indicated. Respiratory care includes breath-stacking techniques, noninvasive ventilation like bilevel positive airway pressure, cough-assist devices, and immunization strategies to reduce infection risk. Disease-modifying therapies comprise exon-skipping antisense oligonucleotides, stop-codon read-through agents for specific mutations, and investigational gene therapies delivering truncated dystrophin via adeno-associated viral vectors, alongside cell-based and genome-editing approaches. Orthopedic interventions address scoliosis and contractures, and psychosocial support and educational accommodations optimize developmental outcomes.

Prognosis and complications

Without intervention, progressive weakness leads to loss of ambulation in childhood, with cardiopulmonary complications driving morbidity and premature mortality; advances in cardiac and respiratory care have extended life expectancy into the third decade and beyond for many patients. Complications include dilated cardiomyopathy, heart failure, respiratory failure, recurrent lower respiratory tract infections, scoliosis-related compromise, venous thromboembolism, and treatment-related adverse effects such as steroid-induced osteoporosis and growth suppression. Regular surveillance and timely interventions can mitigate complications and improve longevity and quality of life.

Epidemiology

The condition affects approximately 1 in 3,500 to 1 in 5,000 live male births worldwide, with prevalence estimates varying by region and ascertainment; carrier females may show milder manifestations such as cardiomyopathy. Incidence and prevalence are reported across diverse populations in epidemiologic studies spanning North America, Europe, Asia, and Africa, and newborn screening pilots and registries have informed surveillance and care planning.

History and research advancements

Descriptions of progressive childhood muscular wasting date to 19th-century clinicians, and the eponym recognizes pioneering observations and characterization in early neurology; elucidation of the dystrophin gene in the 1980s revolutionized molecular diagnosis and therapeutic research. Subsequent milestones include development of corticosteroid regimens, cardiac and respiratory management protocols, approval of mutation-specific therapies, and ongoing clinical trials of gene replacement, exon-skipping, read-through compounds, and genome-editing strategies. Collaborative research networks, patient advocacy organizations, and regulatory pathways have accelerated translational efforts and newborn screening initiatives, shaping contemporary standards of care.

Category:Genetic disorders